یَـٰۤأَیُّهَا ٱلَّذِینَ ءَامَنُوۤا۟ إِذَا ضَرَبۡتُمۡ فِی سَبِیلِ ٱللَّهِ فَتَبَیَّنُوا۟ وَلَا تَقُولُوا۟ لِمَنۡ أَلۡقَىٰۤ إِلَیۡكُمُ ٱلسَّلَـٰمَ لَسۡتَ مُؤۡمِنࣰا تَبۡتَغُونَ عَرَضَ ٱلۡحَیَوٰةِ ٱلدُّنۡیَا فَعِندَ ٱللَّهِ مَغَانِمُ كَثِیرَةࣱۚ كَذَ ٰلِكَ كُنتُم مِّن قَبۡلُ فَمَنَّ ٱللَّهُ عَلَیۡكُمۡ فَتَبَیَّنُوۤا۟ۚ إِنَّ ٱللَّهَ كَانَ بِمَا تَعۡمَلُونَ خَبِیرࣰا
التفسير التبليغي
(O you who have believed, when you journey forth [to fight] in the cause of Allah, investigate carefully, and do not say to one who offers you [the greeting of] peace, "You are not a believer," seeking the transient goods of worldly life; for with Allah are many gains. Thus were you yourselves before, then Allah conferred His favor upon you. So investigate carefully. Indeed Allah is ever, with what you do, Acquainted.)
(وَلا تَقُولُوا لِمَنْ أَلْقَى إِلَيْكُمْ السَّلامَ) meaning: to one who surrenders to you, submitting to Allah with monotheism, acknowledging your religion to you.
(وَلا تَقُولُوا لِمَنْ أَلْقَى إِلَيْكُمْ السَّلامَ) And do not say to one who surrenders to you and does not fight you, showing you that he is of your religion and your call, "You are not a believer," so you kill him, (تَبْتَغُونَ عَرَضَ الْحَيَاةِ الدُّنْيَا) seeking the transient goods of worldly life. For with Allah are many gains from His provision, favors, and blessings, and these are better for you.
(كَذَلِكَ كُنْتُمْ مِنْ قَبْلُ) before Allah honored His religion, (فَمَنَّ اللَّهُ عَلَيْكُمْ فَتَبَيَّنُوا).
(كَذَلِكَ) you were disbelievers like them, (فَمَنَّ اللَّهُ عَلَيْكُمْ فَتَبَيَّنُوا).
(فَمَنَّ اللَّهُ عَلَيْكُمْ) with repentance from your killing of this person whom you killed and whose property you took after he offered you peace, (فَتَبَيَّنُوا).
(فَتَبَيَّنُوا) So do not rush to kill someone whom you intended to kill, whose matter of Islam is unclear to you. For perhaps Allah has bestowed upon him Islam, similar to that which He bestowed upon you, and guided him to the like of what He guided you to of faith.
(فَتَبَيَّنُوا) So be deliberate in killing someone whose matter is obscure to you, whose true Islam or disbelief you do not know, and do not rush to kill someone whose matter is unclear to you.
(فَتَبَيَّنُوا) from "al-tabayyun," meaning deliberation, consideration, and investigation until it becomes clear.
Source: التفسير التبليغي