It was narrated that Ibn "Abbas said:

A man of Banu Sulaim passed by a group of the Companions of the Messenger of Allah(ﷺ), driving some sheep of his, and greeted them with salam. They said: He only greeted us with salam so as to protect himself from us. So they went and killed him, and brought his sheep to the Messenger of Allah (ﷺ). Then this verse was revealed: “O you who believe! When you go (to fight) in the Cause of Allah, verify (the truth)." [an-Nisa" 4:94].