Surah An-Nisa, ayah 94

يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓاْ إِذَا ضَرَبۡتُمۡ فِي سَبِيلِ ٱللَّهِ فَتَبَيَّنُواْ وَلَا تَقُولُواْ لِمَنۡ أَلۡقَىٰٓ إِلَيۡكُمُ ٱلسَّلَٰمَ لَسۡتَ مُؤۡمِنٗا تَبۡتَغُونَ عَرَضَ ٱلۡحَيَوٰةِ ٱلدُّنۡيَا فَعِندَ ٱللَّهِ مَغَانِمُ كَثِيرَةٞۚ كَذَٰلِكَ كُنتُم مِّن قَبۡلُ فَمَنَّ ٱللَّهُ عَلَيۡكُمۡ فَتَبَيَّنُوٓاْۚ إِنَّ ٱللَّهَ كَانَ بِمَا تَعۡمَلُونَ خَبِيرٗا ٩٤

Yā'ayyuhal-ladhīna āmanū idhā darabtum fī sabīlillāhi fatabayyanū walā taqūlū liman alqā ilaykumus-salāma lasta mu'minan tabtaghūna 'aradal-hayawātid-dunyā fa'indallāhi maghānimu kathīratun kadhālika kuntum min qablu famannallāhu 'alaykum fatabayyanū innallāha kāna bimā ta'malūna khabīrā

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.