The following are views from various Muslim scholars and individuals on ISIS. The list by no means represents any endorsement of those listed by Islam21c.
Some conclusive scholarly opinions concerning ISIS and their actions
The Syrian conflict has raged on, leaving conscious Muslims experiencing an agonising dilemma: to watch helplessly while thousands are oppressed and killed or to help with whatever is in their capacity. A number of Muslim youth have opted to join the revolt, offering their lives to the cause. This has prompted the government to adopt or suggest punitive actions against them citing fear that they would become ‘radicalised’. Years prior to this rather uncertain position assumed by the British government, scholars in Syria and abroad had warned foreigners of travelling to fight in Syria. This was not due to fears of ‘radicalisation’ as these are not substantiated by any empirical evidence, but rather for concerns that the course of the revolution would be hampered since manpower was never required as much as financial and medical resources.
Years into the mass uprising, certain elements sprung up and spread in the revolution, that severely stalled progress against the Syrian regime. In addition to this, certain groups began perpetrating crimes against Syrian fighters through internal provocation and conflict and through targeting aid workers and civilians, whilst following a warped reading into Islam unrecognised by countless Syrian and international scholars.  Scholars had previously communicated their position to the masses, but their incapacity to take these scholars seriously developed the catastrophe the scholars had warned of. The catastrophe culminated in predominantly misinformed outsiders bolstering the strength of the ‘Islamic State of Iraq and the Levant’ (ISIS), duped by the group’s buzz-words (Khilāfah, Bay’ah, Amīr al-Mu’minīn, Hijrahand so on). In reality, if ISIS are not part of Assad’s regime as some claim, they have either been severely infiltrated by the regime or their ideology is starkly unrelated to Islam and critically misguided.
ISIS have not only weakened the fighters in Syria against Bashar, but have murdered arbitrators and committed heinous crimes against Muslims. The regime has benefited greatly by the presence of ISIS, even avoiding them in pursuit and attack. ISIS have furthermore shackled the progress of some of the most effective Islamic rebel groups by waging war on them for their refusal to ‘pledge allegiance’ to them and to their warped ideology. The government and media suggest that many of those who have gone to fight in Syria have joined ISIS while recent videos might be seen to confirm these claims. Assuming these claims to be accurate, it becomes binding upon those who are sincere in yearning for an end to the oppression to reveal the unmistakable reality.
Sadly, many eager individuals do not recognise the authority of Syria’s scholars, dismissing their views while accusing others of being “politicised”. Who did they follow and what did they risk? No doubt the scale of the crisis in Syria is unparalleled, thus what is at stake for those who travel there is most probably death. Death will lead to Paradise or the Hellfire. For those who opted to join ISIS, on what basis and through what justification are they willing meet Allāh when this faction has shed the blood of thousands unjustly? The question remains, did these individuals refer to the Book of Allāh, the injunctions of the Messenger salla Allāhu ‘alayh wasalam and the guidance of our leaders in understanding and faith, the recognised scholars of Islam, before embarking on this ākhirah-focused risk? Those who truly care for the course of the revolution and desire that it achieves the best end will categorically stop at the injunction of Allāh if nothing else. If our pride fails to lend Syrian scholars their worth, take the following international statements and verdicts regarding ISIS, issued by the following diverse list of scholars. 
Most scholars used the Arabic abbreviation ‘Dā’esh’ in reference to ISIS. ‘Dā’esh’ has been substituted for ISIS for the convenience of the reader.
Sheikh Abu Abdullah al-Masry:
Sheikh al-Masry was previously a member of ISIS but withdrew from them on the basis of their ideology and methodology. He justifies his withdrawal by mentioning ISIS’ defamation of the people of Syria, claiming they were ideologically misguided, asking how this could be the case if the Prophet salla Allāhu ‘alayh wasalam said: ”If the people of Shaam corrupt, there is no good in you.” The Sheikh adds:
“The behaviour of many elements in ISIS including leaders consistently is offensive towards the people of Syria and itsMujāhidīn, accusing them of misguidance in belief and action.” He further said: “They moreover repeatedly accuse the people of Syria and the Free Syrian Army (FSA) of disbelief (Kufr).” The Sheikh also argued that ISIS cannot be theoretically classified as Khawārij although practically this may be the case since they throw around accusations of disbelief without evidence and without understanding the gravity of such a charge. Rather, they may indict someone as a disbeliever merely on the grounds of disagreeing with them. Many of them believe that the people of Syria are originally apostates before creating justifications to this effect, raising weapons in their faces for the most trivial of matters.
Sheikh Abdul Aziz al-Tarifi:
Sheikh al-Tarifi is a Researcher in the Ministry of Islamic Affairs in Riyadh. The Sheikh is deeply erudite in the sciences of Islam, known for his profound ability to retrieve evidences and issue meticulous verdicts. Among his teachers are Sheikh Abdul Aziz b. Abdullah b. Baz, Faqih Abdullah b. Abdul Aziz b. Aqeel and Sheikh Muhammad b. al-Hasan al-Shanqeeti. The sheikh has an extensive number of printed works. He states:
“It is impermissible for anyone to make his group or party a milestone against which loyalty and hostility are measured, such that he believes that allegiance and leadership should belong to him exclusively. Whoever believes that sole allegiance applies to him (or his party) from amongst all Muslims, then upon him apply the words of Allāh: “Verily, those who divide their religion and break up into sects (all kinds of religious sects), you (O Muhammad salla Allāh ‘alayh wasalam) have no concern in them in the least.”“ The Sheikh added: “it is incorrect that while in a state of fighting and factions that one group should request individual and general allegiance and all that it entails. The allegiance is to the Jihād, constancy, patience and reform. It is incorrect that one individual who leads a particular faction to call himself Amīr al-Mu’minīn (the leader of the Believers), rather he should call himself the leader of the army, the battalion or the battle. General leadership is determined by Shūrā(consultation) between believers, not for an individual to assume. Titles cause exclusivity that can lead to dispute, conflict, strife and evil… [Therefore], participating with ISIS so long as it does not agree with the law of Allāh, independent of it is impermissible.”
Sheikh Sulaiman b. Nasser al-Alwan:
The Sheikh began pursuing knowledge at the age of fifteen. He has written comprehensive explanations of Hadīth books including Sahīh al-Bukhari, Jāmi’ Abū Issa al-Tirmidhi, Sunan Abī Dāwūd, Muwata’ Mālik among many others. He quotes:
“Al-Baghdadi is not the Khalīfahof the Muslims for him to do whatever he pleases; rather he is a leader of a faction. Requesting a pledge of allegiance, killing those who refuse is the action of an aggressor, not the action of a person of good and righteousness.” He further said: “If his own leader does not agree with his actions, how can he expect allegiance from others?”
Sheikh Muhammad b. Salih al-Munajjid:
Sheikh Mohammad al-Munajjid is a renowned scholar of Islam with an array of recognised works (including IslamQA.com). His teachers include Sheikh Abdul Aziz b. Abdullah b. Baz, Sheikh Abdullah b. Abdul Rahman b. Jibreen and Sheikh Abdul Rahman al-Barrak. He is currently the imām of the Mosque of Omar b. Abdul Aziz al-Khobar. He says:
“If a group thinks, for example, that it has established the Islamic state, its leader is the ‘Leader of the Believers’, that he should be listened to and obeyed by everyone, that anyone not under his command has rebelled against him, that [this ‘state’] has the authority to draw up borders, elect leaders over towns, that it has authority over public wealth, petrol, wheat and so on, that others should forcefully submit to them while they can stop whoever they want, that they have the sole authority of establishing Islamic courts and judges and that every court besides theirs is void, it has deviated. This will no doubt create competition over control of regions and eventually lead to a great Fitnah and bloodshed.”
Sheikh Abu Muhammad al-Maqdisi:
Sheikh Muhammad al-Maqdisi is considered the guide of the ‘Jihadist Salafist’ movement in Jordan. His name is Issam Barqawi but is famously known as Abu Muhammad al-Maqdisi. Far from siding with ISIS, he says in a letter to the Mujāhidīn of Syria after hearing of ISIS and their behaviour with other fighters:
“…and we do not feel ashamed to declare that we are free from the actions of those who dare spill the blood of Muslims whoever they may be.” He further added: “How can you be expected to accommodate all Syrians including Christians and other sects [if you cannot even accommodate other Muslims]?”
Dr. Hassan Saleh b. Hamid:
Dr. Hassan Saleh has a PhD in the principles of Fiqh and Sharī’ah, he is the Director of the Institute of Higher Islamic Education at the Umm Al-Qura University in Makkah and is a Member of the (Islamic) Advisory council. He says:
“No one going to Syria to fight is excused to be part of al-Baghadi’s faction for even a moment… they are a faction that brings Fitnah, whenever they are called to a court for religious arbitration they turn away and whenever a truce is declared, they reignite the war.”
Sheikh Abdul Aziz al-Fawzan:
Sheikh Abdul Aziz al-Fawzan is a member of the Council for Human Rights, a Professor in Islamic Jurisprudence and the Head of the Department of Comparative Jurisprudence at the Islamic University of Imam Muhammad b. Saud in Saudi Arabia. He says:
“ISIS is a rogue, external criminal organisation. Whoever knows of what afflicted us in Iraq and Afghanistan and the blood that was spilled unjustly at the hands of some ignorant individuals in our nation will understand the gravity of what is happening in Syria.”
Dr. Abdul Karim Bakkar:
Dr. Abdul Karim Bakkar is one of the leading authors in the field of education and Islamic thought, who seeks to provide a deep-rooted analysis into matters concerning Islamic civilisation, renaissance and Da’wah. He has more than 40 books in this area. Dr. Abdul Karim Bakkar is a member of the Advisory Board for the Islam Today magazine (Riyadh). He says:
“I met a number of students of knowledge and Islamic jurists returning from Syria. I swear by the One besides whom there is no god that the only thing they spoke about were the repulsive actions of ISIS and their crimes. ISIS and the Assad regime are two faces of one evil.”
Dr. Shafi al-Ajmi:
Dr. Al-Ajmi sought knowledge under the supervision of Sheikh Muhammad b. Saalih and Sheikh Yahya al-Yahya. He studied at the University of Imam Muhammad b. Saud and is now the Imām of al-Ghazali Mosque in Kuwait.He quotes:
“I have not heard of a single scholar inside or outside of Syria who has praised this faction, had good suspicion of them or defended them, rather they have unanimously agreed that they are aggressors. Al-Baghdadi’s aim, since entering Syria is to weaken the fighters and he has indeed weakened al-Nusra Front and Ahraar al-Shaam and continues to do so.”
Sheikh Abu Basir al-Tartusi:
Sheikh Abu Basir al-Tartusi has played the effective role of the Syrian revolution’s Mufti. It is said that Sheikh al-Tartusi was the first Arab fighter to travel to Afghanistan in 1981, accompanying Abdullah Azzam on one of his trips. He has authored many books and is the founder of several of the revolution’s coordination groups. He says:
“The group known as ISIS are from the fanatical Khawārij, rather they have surpassed theKhawārij in many of their characteristics and actions, combining between fanaticism, aggression, hostility and shedding inviolable blood.” He further said: “We call upon all sincere individuals who have been fooled by them while still with this misguided group to severe their ties with it and to declare their freedom from it and its actions.”
Sheikh Abdullah Saad:
The Sheikh and notable Muhadtih Abdullah b. Abdul Rahman b. Mohammed Al-Saad Al-Mutairi is one of those at the forefront of 20thand 21st century Muslim scholars. His teachers include, Sheikh Abdul Aziz b. Baz, Sheikh Mohammed b. Saalih and Sheikh Abdullah b. Abdul Rahman al-Jibreen. He has authored tens of books and has explanations of Bukhāri, Sunan Abī Dāwūd, Jāmi’ al-Tirmithi and others.He says:
“I plea to whoever joined this faction (ISIS) to leave it and move away from it, and for its leaders to return to the truth and to repent to Allāh from the grave mistakes they have fallen into…”
Sheikh Abdullah al-Mahiseny:
Sheikh al-Mahiseny is a specialist in Islamic Jurisprudence, acquiring a PhD in Comparative Fiqh in the subject: “Rulings Concerning War Refugees in Islamic Jurisprudence.” He says:
“By Allāh, I have never witnessed the scholars who speak about matters of Jihād agree on criticising and opposing a Muslim movement as they have agreed on condemning ISIS.” Sheikh Mahiseny concluded by saying: “I implore you by Allāh O Baghdadi to allow a general Islamic court mediate to uphold the injunctions of Allāh.”
Sheikh Adnan Mohammed al-Aroor:
Sheikh Adnan al-Aroor is currently the Director of Research and Publishing in Riyadh. He grew up seeking knowledge in Syria under several scholars including Sheikh al-Albani and Sheikh b. Baz. He is one of the most notable scholarly icons of the Syrian revolution and has a multitude of published works. Sheikh al-Aroor says, directing his question at ISIS:
“Did Allāh set conditions that must be met before accepting that the Qur’ān arbitrate [in the affairs of difference]? Then where did you get these conditions [that you set] from? Why do you leave military fronts such as Homs and dedicate your efforts to the areas near the Turkish borders? … Who are the people of religious authority (ahl al-hal wal-’aqd) who you consulted before establishing your ‘state’? Do you aim to overthrow the sectarian dictator or to fight others [who want to achieve this]? … What is your Islamic proof that justifies your pledge to someone unknown?” He furthermore states: “ISIS are either Khawārijor infiltrated by the [Syrian] regime. It is composed of three groups of people: brutal Takfīrīs, wicked infiltrators and people deceived by them.”
The Scholars of Aleppo Front:
The Scholars of Aleppo Front issued a statement encouraging the sincere members of ISIS to leave this faction and join the legitimate revolutionary forces in Syria for the crime that has been perpetrated by this group, including:
Accusations of disbelief (takfīr), their shedding of inviolable blood without a second thought, kidnappings and documented armed robberies of weapons and ammunition from other rebel factions, their refusal to allow theSharī’ah to arbitrate between them and the other factions and sowing the seeds of discord between fighers. ISIS’ takfīrsometimes extend to the entire population of Syria. This includestakfīr boldly levelled at the Free Syrian Army, accusing Ahraar al-Shaam that they are misguided ‘Surūrīs’ and that al-Nusra Front have defied their alleged ‘Khalīfah’.
A Joint Statement of 47 Scholars in Saudi Arabia
Including Al-Ghunaymaan, Al-‘Umar, Al-Mahmoud and Al-Jalali Al-Mahmoud
The joint statement asserted that it is impermissible and of tyranny for one faction to impose itself as the only holder of legitimacy and that it is necessary that all other groups pledge allegiance to it without consulting the Muslims, otherwise they become of the Khawārij and their blood becomes permissible. It argued that this is the main reason for divisions and internal fighting. Sheikh Hamoud b. Ali al-Omari added: “The reality of the matter is, every drop of blood shed between the (rebel) factions in Syria is due to al-Baghdadi’s refusal to allow the Sharī’ah to arbitrate while implementing his own innovated Sharī’ah.”
There is no act, the punishment for which has been mentioned more sternly than that of killing a believer intentionally where a collection of five severe retributions have been listed:
“But whoever kills a believer intentionally – his recompense is Hell, wherein he will abide eternally, and Allāh has become angry with him and has cursed him and has prepared for him a great punishment.”
Above are only some of the verdicts issued against ISIS by Muslim scholars. Such an agreement between scholars, analysts and intellectuals across the board should shake the heart of any individual who has participated in hampering the revolutionary effort while imposing an innovated ideology on its people. This neither pleases Allāh nor is it to the betterment of Syria. Syrians are in no need of further repression. Sincere individuals who have joined ISIS believing it endorses the true purpose of Islam should rush to change course and avoid further gambling with their permanent abode, and with a Syrian future that balances on a knife’s edge.
This article is presented for information purposes, and is not an official view of MRDF or Islam21c.
 http://www.almokhtsar.com/news/Title/author: أقوال العلماء والدعاة في داعش / إبراهيم بن عبد الرحمن التركي
 Al-Qur’ān 6:159