Allah said,
[وَقَـتِلُوهُمْ 
حَتَّى لاَ تَكُونَ فِتْنَةٌ وَيَكُونَ الدِّينُ كُلُّهُ لِلهِ]
(And fight them until there is no more Fitnah, and the religion will all be 
for Allah alone.)
Al-Bukhari recorded that a man came to Ibn `Umar and said to him, "O Abu 
`Abdur-Rahman! Why do you not implement what Allah said in His Book,
[وَإِن طَآئِفَتَانِ 
مِنَ الْمُؤْمِنِينَ اقْتَتَلُواْ]
(And if two parties (or groups) among the believers fall to 
fighting...)[49:9]. What prevents you from fighting as Allah mentioned in His 
Book'' Ibn `Umar said, "O my nephew! I prefer that I be reminded with this Ayah 
rather than fighting, for in the latter case, I will be reminded by the Ayah in 
which Allah, the Exalted and Most Honored, said,
[وَمَن يَقْتُلْ 
مُؤْمِناً مُّتَعَمِّداً]
(And whoever kills a believer intentionally...) [4:93]''
The man said, "Allah, the Exalted, said,
[وَقَـتِلُوهُمْ 
حَتَّى لاَ تَكُونَ فِتْنَةٌ]
(And fight them until there is no more Fitnah...).'' Ibn `Umar said, "We did 
that during the time of the Messenger of Allah, when Islam was weak and the man 
would be tried in religion, either tormented to death or being imprisoned. When 
Islam became stronger and widespread, there was no more Fitnah.'' When the man 
realized that Ibn `Umar would not agree to what he is saying, he asked him, 
"What do you say about `Ali and `Uthman'' Ibn `Umar replied, "What do I say 
about `Ali and `Uthman! As for `Uthman, Allah has forgiven him, but you hate 
that Allah forgives him. As for `Ali, he is the cousin of the Messenger of Allah 
and his son-in-law,'' and he pointed with his hand saying, "And this is his 
house over there.'' Sa`id bin Jubayr said, "Ibn `Umar came to us and was asked, 
"What do you say about fighting during Fitnah'' Ibn `Umar said, "Do you know 
what Fitnah refers to Muhammad was fighting against the idolators, and at that 
time, attending (or residing with) the idolators was a Fitnah (trial in 
religion). It is nothing like what you are doing, fighting to gain leadership!'' 
All these narrations were collected by Al-Bukhari, may Allah the Exalted grant 
him His mercy. Ad-Dahhak reported that Ibn `Abbas said about the Ayah,
[وَقَـتِلُوهُمْ 
حَتَّى لاَ تَكُونَ فِتْنَةٌ]
(And fight them until there is no more Fitnah...) "So that there is no more 
Shirk.'' Similar was said by Abu Al-`Aliyah, Mujahid, Al-Hasan, Qatadah, 
Ar-Rabi` bin Anas, As-Suddi, Muqatil bin Hayyan and Zayd bin Aslam. Muhammad bin 
Ishaq said that he was informed from Az-Zuhri, from `Urwah bin Az-Zubayr and 
other scholars that
[حَتَّى لاَ تَكُونَ 
فِتْنَةٌ]
(until there is no more Fitnah) the Fitnah mentioned here means, until no 
Muslim is persecuted so that he abandons his religion. Ad-Dahhak reported that 
Ibn `Abbas said about Allah's statement,
[وَيَكُونَ الدِّينُ 
كُلُّهُ لِلهِ]
(and the religion (worship) will all be for Allah alone.) "So that Tawhid is 
practiced in sincerity with Allah.'' Al-Hasan, Qatadah and Ibn Jurayj said,
[وَيَكُونَ الدِّينُ 
كُلُّهُ لِلهِ]
(and the religion will all be for Allah alone) "So that La ilaha illa-llah is 
proclaimed.'' Muhammad bin Ishaq also commented on this Ayah, "So that Tawhid is 
practiced in sincerity towards Allah, without Shirk, all the while shunning all 
rivals who (are being worshipped) besides Him.''
`Abdur-Rahman bin Zayd bin Aslam said about,
[وَيَكُونَ الدِّينُ 
كُلُّهُ لِلهِ]
(and the religion will all be for Allah alone) "So that there is no more Kufr 
(disbelief) with your religion remains.'' There is a Hadith collected in the Two 
Sahihs that testifies to this explanation. The Messenger of Allah said,
«أُمِرْتُ أَنْ 
أُقَاتِلَ النَّاسَ، حَتَّى يَقُولُوا: لَا إِلَهَ إِلَّا اللهُ، فَإِذَا قَالُوهَا 
عَصَمُوا مِنِّي دِمَاءَهُمْ وَأَمْوَالَهُمْ، إِلَّا بِحَقِّهَا، وَحِسَابُهُمْ 
عَلَى اللهِ عَزَّ وَجَل»
(I was commanded to fight against the people until they proclaim, `There is 
no deity worthy of worship except Allah.' If and when they say it, they will 
preserve their blood and wealth from me, except for its right (Islamic penal 
code), and their reckoning is with Allah, the Exalted and Most Honored.)
Also, in the Two Sahihs, it is recorded that Abu Musa Al-Ash`ari said, "The 
Messenger of Allah was asked about a man who fights because he is courageous, in 
prejudice with his people, or to show off. Which of these is for the cause of 
Allah He said,
«مَنْ قَاتَلَ 
لِتَكُونَ كَلِمَةُ اللهِ هِيَ الْعُلْيَا فَهُوَ فِي سَبِيلِ اللهِ عَزَّ 
وَجَل»
(Whoever fights so that Allah's Word is the supreme, is in the cause of 
Allah, the Exalted and Most Honored.)''
Allah said next,
[فَإِنِ 
انْتَهَوْاْ]
(But if they cease), and desist from their Kufr as a result of your fighting 
them, even though you do not know the true reasons why they did so,
[فَإِنَّ اللَّهَ 
بِمَا يَعْمَلُونَ بَصِيرٌ]
(then certainly, Allah is All-Seer of what they do.)
Allah said in similar Ayah,
[فَإِن تَابُواْ 
وَأَقَامُواْ الصَّلَوةَ وَءاتَوُاْ الزَّكَوةَ فَخَلُّواْ سَبِيلَهُمْ]
(But if they repent and perform the Salah, and give Zakah, then leave their 
way free.) [9:5],
[فَإِخوَانُكُمْ فِى 
الدِّينِ]
(...then they are your brethren in religion.) [9:11], and,
[وَقَـتِلُوهُمْ 
حَتَّى لاَ تَكُونَ فِتْنَةٌ وَيَكُونَ الدِّينُ للَّهِ فَإِنِ انتَهَواْ فَلاَ 
عُدْوَنَ إِلاَّ عَلَى الظَّـلِمِينَ ]
(And fight them until there is no more Fitnah and the religion (worship) is 
for Allah (alone). But if they cease, let there be no transgression except 
against the wrongdoers.) [2:193]
It is recorded in the Sahih that the Messenger of Allah said to Usamah bin 
Zayd when he overpowered a man with his sword, after that man proclaimed that 
there is no deity worthy of worship except Allah;
«أَقَتَلْتَهُ بَعْدَ 
مَا قَالَ لَا إِلَهَ إِلَّا اللهُ؟ وَكَيْفَ تَصْنَعُ بِلَا إِلَهَ إِلَّا اللهُ 
يَوْمَ الْقِيَامَةِ؟»
(Have you killed him after he proclaimed, `La Ilaha Illallah' What would you 
do with regard to `La Ilaha Illallah' on the Day of Resurrection.)
Usamah said, "O Allah's Messenger! He only said it to save himself.'' The 
Messenger replied,
«هَلَّا شَقَقْتَ 
عَنْ قَلْبِهِ؟»
(Did you cut his heart open)
The Messenger kept repeating,
«مَنْ لَكَ بِلَا 
إِلهَ إِلَّا اللهُ يَوْمَ الْقِيَامَةِ؟»
(What would you do with regard to `La Ilaha Illallah' on the Day of 
Resurrection) until Usamah said, "I wished I had embraced Islam only that day.'' 
Allah said next,
[وَإِن تَوَلَّوْاْ 
فَاعْلَمُواْ أَنَّ اللَّهَ مَوْلاَكُمْ نِعْمَ الْمَوْلَى وَنِعْمَ النَّصِيرُ 
]
(And if they turn away, then know that Allah is your protector, an excellent 
protector, and an excellent helper!)
Allah says, if the disbelievers persist in defying and fighting you, then 
know that Allah is your protector, master and supporter against your enemies. 
Verily, what an excellent protector and what an excellent supporter.
[وَاعْلَمُوا 
أَنَّمَا غَنِمْتُم مِّن شَىْءٍ فَأَنَّ للَّهِ خُمُسَهُ وَلِلرَّسُولِ وَلِذِى 
الْقُرْبَى وَالْيَتَـمَى وَالْمَسَـكِينِ وَابْنِ السَّبِيلِ إِن كُنتُمْ 
ءَامَنْتُم بِاللَّهِ وَمَآ أَنزَلْنَا عَلَى عَبْدِنَا يَوْمَ الْفُرْقَانِ يَوْمَ 
الْتَقَى الْجَمْعَانِ وَاللَّهُ عَلَى كُلِّ شَىْءٍ قَدِيرٌ ]
(41. And know that whatever of war booty that you may gain, verily, one-fifth 
of it is assigned to Allah, and to the Messenger, and to the near relatives (of 
the Messenger), the orphans, the poor, and the wayfarer, if you have believed in 
Allah and in that which We sent down to Our servant on the Day of Criterion, the 
Day when the two forces met; and Allah is able to do all things.)