An-Nisaa 4:94

O you who believe, when you go to fight in the way of Allah, make sure [who you fight]; and do not say to someone who offers you the greetings of peace, “You are not a believer”[70] – seeking gains of the life of this world, while Allah has abundant gains. You were in the same position before, then Allah blessed you [with Islam]. Therefore make sure, for Allah is All-Aware of what you do.

[70] This is someone who withholds from fighting and declares that he is a believer.

O you who have believed, when you go forth [to fight] in the cause of Allāh, investigate; and do not say to one who gives you [a greeting of] peace, "You are not a believer,"[211] aspiring for the goods of worldly life; for with Allāh are many acquisitions. You [yourselves] were like that before; then Allāh conferred His favor [i.e., guidance] upon you, so investigate. Indeed Allāh is ever, of what you do, Aware.

[211] Do not assume that he pretends Islām merely in order to save himself, for he may be sincere in faith.

94. O you who believe! When you go (to fight) in the Cause of Allâh, verify (the truth), and say not to anyone who greets you (by embracing Islâm): "You are not a believer"; seeking the perishable goods of the worldly life. There are much more profits and booties with Allâh. Even as he is now, so were you yourselves before till Allâh conferred on you His Favours (i.e. guided you to Islâm), therefore, be cautious in discrimination. Allâh is Ever Well-Aware of what you do.

O ye who believe! When ye go forth (to fight) in the way of Allah, be careful to discriminate, and say not unto one who offereth you peace: "Thou art not a believer," seeking the chance profits of this life (so that ye may despoil him). With Allah are plenteous spoils. Even thus (as he now is) were ye before; but Allah hath since then been gracious unto you. Therefore take care to discriminate. Allah is ever Informed of what ye do.