In The Name of Allah, The Most Merciful, The Bestower of Mercy.

Allah, The Most High, said:

يَا أَيُّهَا الَّذِينَ آمَنُوا إِذَا ضَرَبْتُمْ فِي سَبِيلِ اللَّهِ فَتَبَيَّنُوا وَلَا تَقُولُوا لِمَنْ أَلْقَىٰ إِلَيْكُمُ السَّلَامَ لَسْتَ مُؤْمِنًا تَبْتَغُونَ عَرَضَ الْحَيَاةِ الدُّنْيَا فَعِندَ اللَّهِ مَغَانِمُ كَثِيرَةٌ ۚ كَذَٰلِكَ كُنتُم مِّن قَبْلُ فَمَنَّ اللَّهُ عَلَيْكُمْ فَتَبَيَّنُوا ۚ إِنَّ اللَّهَ كَانَ بِمَا تَعْمَلُونَ خَبِيرًا

O you who believe! When you go (to fight) in the Cause of Allah, verify (the truth), and say not to anyone who greets you (by embracing Islam): “You are not a believer”; seeking the perishable goods of the worldly life. There are much more profits and booties with Allah. Even as he is now, you (yourselves) were like that before; then Allah conferred on you His Favours (i.e. guided you to Islam), therefore, verify. Allah is Ever Well-Aware of what you do. [An-Nisa 94]

He (Allah), The Most High, commands His believing servants that when they proceed for Jihad upon His path and seeking His pleasure, they should seek clarification and verification regarding the ambiguous matters. For indeed, the affairs are of two categories: those that are clear and those that are unclear. The clear and evident matters do not need verification and clarification because that is self-evident. As for the ambiguous matters – the unclear matters, then indeed, a person needs to verify and clarify regarding them in order to know whether to pursue or not. For indeed verification in these matters bring many benefits and prevents great evils by way of which is known the (upright) religion of a person, his intellect and self-possession, as opposed to the one who rushes into matters at their onset before their their rulings are clarified for him, for indeed this leads to that which is not befitting (or permissible) as happened to those whom Allah admonished in the verse when they failed to verify and killed those that greeted them with the salutation of peace- who had spoils of war in their possession or someone else’s wealth- thinking that it was justified to kill them. This was a (grave) mistake and due to this, Allah reproached, saying:

وَلَا تَقُولُوا لِمَنْ أَلْقَى إِلَيْكُمُ السَّلَامَ لَسْتَ مُؤْمِنًا تَبْتَغُونَ عَرَضَ الْحَيَاةِ الدُّنْيَا فَعِنْدَ اللَّهِ مَغَانِمُ كَثِيرَةٌ

And say not to anyone who greets you (by embracing Islam): “You are not a believer”; seeking the perishable goods of the worldly life. There are much more profits and booties with Allah.

Meaning: Do not let the transient and little things (of this worldly life) make you commit what is not permissible (or befitting), thus, you miss out on the abundant, everlasting rewards that Allah are with Allah, for that which is with Allah is better and everlasting.

In this is a demonstration that it is obligated to a servant of Allah that when he perceives the urges of his soul inclining towards a state wherein it desires (something), while it is harmful for his soul, he should remind it regarding that which Allah has prepared for the one who forbids his soul from its (vain) desires and and gives precedence to Allah’s Pleasure over the pleasure of his soul, for indeed in this is an encouragement for the soul to fulfil Allah’s command, even if that is difficult for it. Then He (Allah- The Most High) reminded them of their initial situation before they were guided to Islam: [كَذَلِكَ كُنْتُمْ مِنْ قَبْلُ فَمَنَّ اللَّهُ عَلَيْكُمْ- you (yourselves) were like that before; then Allah conferred on you His Favours (i.e. guided you to Islam).

Meaning: Just as He (Allah) guided you after your (state of) misguidance, similarly He can guide others. And just as guidance came to you little by little, similarly is the case for other than yourselves. Thus, the observation of the person- who has accomplished the obligatory and recommended aspects of faith- regarding his initial deficient state, his dealing with the one who is in a similar situation based on what he knows regarding his initial situation, and calling him to (guidance) through wisdom and fine admonition, is one of the greatest means of benefiting himself and the other person. Due to this, He (Allah) repeated the command [فَتَبَيَّنُوا – Therefore, verify].

When it is the case that one who embarks upon Jihad in the path of Allah and to strive against Allah’s enemies – having prepared in various ways to confront them- is commanded to verify when someone greets him with the statement of peace, while there is a strong indication that he (merely) greeted with peace in order to protect himself from being killed and out of fear for himself, then indeed this demonstrates the command to verify and seek clarification in all situations where there is some type of ambiguity, so the person verifies in this situation until the matter becomes clear to him and what is upright and correct is clarified.

إِنَّ اللَّهَ كَانَ بِمَا تَعْمَلُونَ خَبِيرًا

Allah is Ever Well-Aware of what you do.

He will recompense everyone according to their actions and intentions.

An Excerpt from Tafsir As-Sadi. Slightly paraphrased