Aal-i-Imraan 3:28

Let not the believers take disbelievers as allies instead of believers, for whoever does so has nothing to do with Allah at all, except as a protective measure to save yourself from them[12]. And Allah warns you of Himself, and to Allah is the final return.

[12] Upon fearing harm from the disbelievers, Muslims are given license to placate them with their tongues, as long as their hearts are firm in Faith.

Let not believers take disbelievers as allies [i.e., supporters or protectors] rather than believers. And whoever [of you] does that has nothing [i.e., no association] with Allāh, except when taking precaution against them in prudence.[122] And Allāh warns you of Himself, and to Allāh is the [final] destination.

[122] When fearing harm from an enemy, the believer may pretend as long as his heart and intention are not affected.

28. Let not the believers take the disbelievers as Auliyâ (supporters, helpers) instead of the believers, and whoever does that will never be helped by Allâh in any way, except if you indeed fear a danger from them. And Allâh warns you against Himself (His punishment)[4], and to Allâh is the final return.

[4] (V.3:28) The Statement of Allâh عز وجل "But Allâh warns you against Himself (i.e. His Punishment)." (3:28).
Narrated ‘Abdullâh رضي الله عنه: The Prophet صلى الله عليه وسلم said, "There is none who has a greater sense of Ghairah * than Allâh, and for that reason He has forbidden Al-Fawâhish , (the shameful deeds and sins, e.g. illegal sexual intercourse). And there is none who likes to be praised more than Allâh does." (Sahih Al-Bukhâri, Vol.9, Hadîth No.500).
* Ghairah: a feeling of great fury and anger when one’s honour and prestige are injured or challenged.

Let not the believers take disbelievers for their friends in preference to believers. Whoso doeth that hath no connection with Allah unless (it be) that ye but guard yourselves against them, taking (as it were) security. Allah biddeth you beware (only) of Himself. Unto Allah is the journeying.