Begin with a quiet moment of remembrance.

يَٰٓأَيُّهَا ٱلَّذِينَ ءَامَنُوٓا۟ إِذَا ضَرَبْتُمْ فِى سَبِيلِ ٱللَّهِ فَتَبَيَّنُوا۟ وَلَا تَقُولُوا۟ لِمَنْ أَلْقَىٰٓ إِلَيْكُمُ ٱلسَّلَٰمَ لَسْتَ مُؤْمِنًۭا تَبْتَغُونَ عَرَضَ ٱلْحَيَوٰةِ ٱلدُّنْيَا فَعِندَ ٱللَّهِ مَغَانِمُ كَثِيرَةٌۭ ۚ كَذَٰلِكَ كُنتُم مِّن قَبْلُ فَمَنَّ ٱللَّهُ عَلَيْكُمْ فَتَبَيَّنُوٓا۟ ۚ إِنَّ ٱللَّهَ كَانَ بِمَا تَعْمَلُونَ خَبِيرًۭا

Pickthall English meaning

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.