Al-Ma'idah (5): Verse 51
[The discourse concluded] at the phrase {أولياء} (allies/protectors). Then He began anew, saying: {بعضهم أولياء بعض} (some of them are allies to others).
It is narrated that 'Ubadah ibn al-Samit came to the Messenger of Allah (peace and blessings be upon him) and disavowed his allegiance to the Jews. 'Abdullah ibn Ubayy said: "As for me, I will not disavow them, for I fear the vicissitudes of fortune (the turning of events)." Then this verse was revealed.
The meaning of {لا تتخذوهم أولياء} (Do not take them as allies) is: Do not rely on them for victory or seek their favor (do not show them excessive affection).
Then He said: {ومن يتولهم منكم فإنه منهم} (And whoever of you takes them as allies, then he is surely one of them).
Ibn 'Abbas said: This means he is like them in character. This is a severe warning from Allah and an emphasis on the obligation to shun those who oppose one's religion. A similar statement is His saying: {ومن لم يطعمه فإنه منى} (And whoever does not feed him, then he is from the Fire) (Al-Baqarah: 249).
Then He said: {إن الله لا يهدى القوم الظالمين} (Indeed, Allah does not guide the wrongdoing people).
It is narrated from Abu Musa al-Ash'ari that he said: I said to 'Umar ibn al-Khattab (may Allah be pleased with him): "I have a Christian scribe." He said: "What is wrong with you, may Allah destroy you! Why did you not take a Hanif (a monotheist)? Have you not heard the saying of Allah, the Exalted: {يوقنون} [The verse preceding this one in context is about those who believe in the unseen] {ياأيها الذين ءامنوا لا تتخذوا اليهود والنصارى أولياء} (O you who have believed, do not take the Jews and the Christians as allies)?"
I said: "But he is the guardian/trustee of my writing." He replied: "I will not honor them when Allah has humiliated them, nor will I grant them prestige when Allah has disgraced them, nor will I entrust them with religion when Allah has distanced them."
I said: "The affairs of Basra will not be managed without him." He said: "Let the Christian die, and peace be upon you." Meaning: Suppose he has already died, what will you do afterward? Whatever you would do after his death, do it now and dispense with him by finding someone else.
Verse 52
{فترى الذين فى قلوبهم مرض يسارعون فيهم يقولون نخشى أن تصيبنا دآئرة فعسى الله أن يأتى بالفتح أو أمر من عنده فيصبحوا على مآ أسروا فىأنفسهم نادمين}
(You see those in whose hearts is disease hastening to [ally] them, saying, "We fear a misfortune may befall us." But perhaps Allah will bring the conquest or a decision from Himself, and they will become regretful over what they concealed within themselves.)