Surah 4. An-Nisaa'

126In the early days of Islam, Assalam-u-alaikum (peace be upon you) was a symbol of recognition for Muslims. When a Muslim met another Muslim, he greeted him with this salutation, as if to say, "I belong to your own community; I am your friend and well-wisher. I have nothing but peace and security for you; so you should not show enmity towards me nor fear enmity and harm from me." It was like a "pass-word" used in the army while passing through a line of guards at night so as to discern between friends and foes.

The importance of the salutation of peace as a symbol of recognition was specially great at that time because there was no apparent mark of distinction between a Muslim Arab and a non-Muslim Arab, as they wore the same kind of dress and spoke the semi language. Still a difficulty arose when the Muslims attacked some clan and a local Muslim also became the target of attack. Then he would cry out, Asalam-u-alaikum or La llaha illallah (there is no god but Allah). But the attacking Muslims would suspect him to be a disbeliever who was using the password as a trick merely to save his life. They would, therefore, often kill him and take possession of his belongings as spoils. Although the Holy Prophet would severely admonish the offenders on such occasions, yet there was a recurrence of such incidents. Then Allah solved the difficulty in this verse, which means, "You have no right to judge cursorily that the man, who is declaring himself to be a Muslim, is telling a lie merely to save his life. It is equally possible that he may be speaking the truth, or telling a lie, and one cannot know the reality without making a thorough investigation. Thus, while there is a chance of letting off a disbeliever by accepting his salutations of peace as genuine, there is also the more horrible chance of killing an innocent Believer. In any case, it is far better to let off a disbeliever by mistake than to kill a Reliever by error.

127That is, There was a time when you yourselves were scattered as individuals among different clans of disbelievers. You were then hiding your Islam for fear of oppression and persecution and you could offer no other proof of your Faith except by an oral expression. Now it is the bounty of Allah that you are enjoying community life and are able to raise the banner of Islam against the disbelievers. The right way of showing gratitude to Allah for this bounty is to show kindness and leniency to those Muslims who are still in the same state in which you were before this.