In The Name of Allaah, The Most Merciful, The Bestower of Mercy.
Imaam Abdul Azeez Bin Baaz [may Allaah have mercy upon him] said:
There is no doubt that what is obligated on the rulers and leaders of the Muslims is that they judge by the Islamic Sharee’ah in all their affairs and that they wage war against what is in opposition to it. This is an affair about which the scholars of Islaam hold a consensus and all praise and thanks be to Allaah there is no differing regarding it. The proofs in the Qur’an and Sunnah regarding it are many and well known to the people of knowledge, and from them is the statement of Allaah [Glorified be He]:
فَلَا وَرَبِّكَ لَا يُؤۡمِنُونَ حَتَّىٰ يُحَكِّمُوكَ فِيمَا شَجَرَ بَيۡنَهُمۡ ثُمَّ لَا يَجِدُواْ فِىٓ أَنفُسِہِمۡ حَرَجً۬ا مِّمَّا قَضَيۡتَ وَيُسَلِّمُواْ تَسۡلِيمً۬ا
But no, by your Lord, they can have no Faith, until they make you (O Muhammad) judge in all disputes between them, and find in themselves no resistance against your decisions, and accept (them) with full submission. [Surah An-Nisaa. Aayah 65]
And the statement of Allaah [The Mighty and Majestic]:
يَـٰٓأَيُّہَا ٱلَّذِينَ ءَامَنُوٓاْ أَطِيعُواْ ٱللَّهَ وَأَطِيعُواْ ٱلرَّسُولَ وَأُوْلِى ٱلۡأَمۡرِ مِنكُمۡۖ فَإِن تَنَـٰزَعۡتُمۡ فِى شَىۡءٍ۬ فَرُدُّوهُ إِلَى ٱللَّهِ وَٱلرَّسُولِ إِن كُنتُمۡ تُؤۡمِنُونَ بِٱللَّهِ وَٱلۡيَوۡمِ ٱلۡأَخِرِۚ ذَٲلِكَ خَيۡرٌ۬ وَأَحۡسَنُ تَأۡوِيلاً
O you who believe! Obey Allah and obey the Messenger (Muhammad ), and those of you (Muslims) who are in authority. (And) if you differ in anything amongst yourselves, refer it to Allah and His Messenger, if you believe in Allah and in the Last Day. That is better and more suitable for final determination.
[Surah An-Nisaa. Aayah 59]
And the statement of Allaah [Glorified be He]:
وَمَا ٱخۡتَلَفۡتُمۡ فِيهِ مِن شَىۡءٍ۬ فَحُكۡمُهُ ۥۤ إِلَى ٱللَّهِۚ
And in whatsoever you differ, the decision thereof is with Allah (He is the ruling Judge).
[Surah Ash-Shooraa. Aayah 42]
And the statement of Allaah [Glorified be He]:
أَفَحُكۡمَ ٱلۡجَـٰهِلِيَّةِ يَبۡغُونَۚ وَمَنۡ أَحۡسَنُ مِنَ ٱللَّهِ حُكۡمً۬ا لِّقَوۡمٍ۬ يُوقِنُونَ
Do they then seek the judgement of (the Days of) Ignorance? And who is better in judgement than Allah for a people who have firm Faith. [Surah al-Maa’idah. Aayah 50]
And the statement of Allaah [Glorified be He]:
وَمَن لَّمۡ يَحۡكُم بِمَآ أَنزَلَ ٱللَّهُ فَأُوْلَـٰٓٮِٕكَ هُمُ ٱلۡكَـٰفِرُونَ
And whosoever does not judge by what Allah has revealed, such are the disbelievers – of a lesser degree as they do not act on Allah’s Laws. [Surah Al-Maa’idah. Aayah 44] [Read here when does a person become a disbeliever due to ruling by other than what Allaah has revealed: https://www.abukhadeejah.com/ibn-taymiyyah-and-ibn-baaz-on-judging-by-other-than-the-shareeah/ https://www.abukhadeejah.com/the-meaning-of-taghut-according-to-the-early-scholars/ http://www.salafipublications.com/sps/sp.cfm?subsecID=MNJ05&articleID=MNJ050003&pfriend=
وَمَن لَّمۡ يَحۡڪُم بِمَآ أَنزَلَ ٱللَّهُ فَأُوْلَـٰٓٮِٕكَ هُمُ ٱلظَّـٰلِمُونَ
And whosoever does not judge by that which Allah has revealed, such are the wrong-doers.
[Surah Al-Maa’idah. Aayah 45]
وَمَن لَّمۡ يَحۡڪُم بِمَآ أَنزَلَ ٱللَّهُ فَأُوْلَـٰٓٮِٕكَ هُمُ ٱلۡفَـٰسِقُونَ
And whosoever does not judge by what Allah has revealed (then) such (people) are the rebellious sinners.
[Surah Al-Maa’idah. Aayah 47]
The verses that convey this meaning are many. Indeed, the scholars hold a consensus that the one who claims that judging by other than Allaah’s judgement is better or that guidance other than the Messenger’s guidance is better, then he is an unbeliever, just as they also hold a consensus that the one who claims that it is permissible to act [i.e. worship] outside the Sharee’ah of Muhammad or judge with other than it, then he is misguided and an unbeliever. Therefore, based on what we have mentioned from the Qur’aanic evidences and the consensus of the scholars, the questioner knows that those who call to socialism, communism or the other destructive ideologies that are in opposition to the judgement of Islam are misguided and unbelievers. It is not permissible to place one of them as a khateeb and an Imaam in the mosques of the Muslims and prayer behind them is not valid. [Ref 1] [Must read here: https://www.abukhadeejah.com/ibn-taymiyyah-and-ibn-baaz-on-judging-by-other-than-the-shareeah/ https://www.abukhadeejah.com/the-meaning-of-taghut-according-to-the-early-scholars/ http://www.salafipublications.com/sps/sp.cfm?subsecID=MNJ05&articleID=MNJ050003&pfriend= ]
Separation Between Religion And State
What is Siyaasah? It means to regulate the affairs of the citizens; rules related to behaviour and upright rectification. It has jurisdiction over the individual’s behaviour and the society as a whole, and it involves Islamic jurisprudence by way of which the rulers are facilitated with knowledge and understanding of the rulings related to looking after the affairs of the state, its set-ups and Sharee’ah principles. [Ref 2]
Imaam Muhammad Ibn Saaleh Al-Uthaymeen [rahimahullaah] said:
What is intended by ‘Separation between religion and Siyaasah’ is that the ruler can do what he wants based on what he thinks is a means of fulfilling (responsibilities related to) affairs of the state, whether it agrees with Sharee’ah or not; or even if what he does is based on the judgement of the religion, because the meaning of separation is to distinguish between two things and give them specific definitions. Therefore, in relation to this, the ruler looks at what he considers to be beneficial even if it opposes the Sharee’ah. There is no doubt that this is a false and sinful statement, because the religion itself is Siyaasah and Siyaasah itself is the religion, but what we mean by Siyaasah is the Siyaasah that is based on equity and not oppression. The religion of Islaam came to bring about wellbeing [and upright conduct] for the people in their behaviour towards their Lord and between themselves. It establishes the Rights of Allaah, rights for the people- rights for parents, relatives, wives and the Muslims – in general. And even for non-Muslims, Islam has given them rights that are well-known to the scholars. It laid down the means and conditions for war and peace making, punishments for crimes – some of which are determined by way of specific texts and some are left to the jurisdiction of the ruler, as well as other affairs which clearly shows that Islaam in its entirety is Siyaasah. The root of this word Siyaasah is Saa’is and that is the person who is responsible for looking after the affairs of animals – fulfilling that which brings them wellbeing and repelling that which will harm them. This is Siyaasah.
We find this meaning when we contemplate on affairs of the religion, and that Allaah has legislated – for the servants – things without which humans will not be able to establish [a fruitful, stable, orderly, safe] life, and forbade them from things that will corrupt their state of affairs – either affecting everyone or specific individuals. Therefore, in reality the entire religion is Siyaasah. And we are certain that anyone who separates Siyaasah from the Religion and establishes Siyaasah based on what he sees fit and what he forbids, then indeed his Siyaasah is corrupt, and it will cause more harm than good. If it rectifies one affair based on his limited [or deficient] opinions, then indeed it greatly corrupts from another angle. So, this makes it incumbent that one contemplates on the state of affairs of those who base their Siyaasah on their desires and opinions, and became distanced from the religion of Islaam, you will find -after contemplating – that either all that Siyaasah is corrupt or most of it, and that if it rectifies an affair from one angle, it corrupts from another angle. So, based on this, separation between Siyaasah and Religion is a sinful deed and it is obligated on the one who seeks to rectify himself and others that he does so only based on the religion of Islaam. [Ref 3]
Rebuttal Against The Extremists – Those Who Initiate Rebellion And Bloodshed
Even though ruling by other than the Sharee’ah is a sin, however neither is it allowed to rush and declare that a Muslim ruler is an unbeliever nor can this judgement be given by anyone besides the upright scholars. Also, even if a Muslim ruler is declared an unbeliever by the upright scholars, it does not mean that the Muslims are to remove him from the position of rulership by way of rebellion. Must read articles in the links below:
Ahlus-Sunnah wal-Jamā’ah believe that rebellion against the rulers is forbidden
The Tyranny Of The Rulers, A Reason For Rebellion?
The Meaning of Tāghūt and its Relation to Kufr and Judging the Rulers to be Disbelievers
Shaykh al-Fawzaan: Applying the Label of ‘Kharijite’ to Those Involved in Bombings and Who Resemble the Baatiniyyah and Secret Orders
A Lesson from History: The Kharijite Who Engineered the Slaughter of Sunni Scholars at the Hands of the Ubaydi Baatini Shi’ah
All of the Khārijite Sects Hold the View of Rebellion Against the Oppressive Ruler
[Ref 1: Majmoo Fataawaa Wa Maqaalaat Mutanawwi’ah 1/268]
[Ref 2: See At-taleeq Alaa As-Siyaasah Ash-Shar’iyyah. Slightly paraphrased. Page 5 by Imaam Muhammad Ibn Saaleh al-Uthaymeen (rahimahullaah)]
[Ref 3: https://binothaimeen.net/content/7366. Paraphrased]