An-Nisa' - 4:94

يَا أَيُّهَا الَّذِينَ آمَنُواْ إِذَا ضَرَبْتُمْ فِي سَبِيلِ اللّهِ فَتَبَيَّنُواْ وَلاَ تَقُولُواْ لِمَنْ أَلْقَى إِلَيْكُمُ السَّلاَمَ لَسْتَ مُؤْمِنًا تَبْتَغُونَ عَرَضَ الْحَيَاةِ الدُّنْيَا فَعِندَ اللّهِ مَغَانِمُ كَثِيرَةٌ كَذَلِكَ كُنتُم مِّن قَبْلُ فَمَنَّ اللّهُ عَلَيْكُمْ فَتَبَيَّنُواْ إِنَّ اللّهَ كَانَ بِمَا تَعْمَلُونَ خَبِيرًا
[4:94]
O you who believe! when you go to war in Allah's way, make investigation, and do not say to any one who offers you peace: You are not a believer. Do you seek goods of this world's life! But with Allah there are abundant gains; you too were such before, then Allah conferred a benefit on you; therefore make investigation; surely Allah is aware of what you do.
O ye who believe! When ye go abroad in the cause of Allah, investigate carefully, and say not to any one who offers you a salutation: "Thou art none of a believer!" Coveting the perishable goods of this life: with Allah are profits and spoils abundant. Even thus were ye yourselves before, till Allah conferred on you His favours: Therefore carefully investigate. For Allah is well aware of all that ye 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.