Narrated Zaid bin Thabit:
When the Prophet (ﷺ) went out for (the battle of) Uhud, some of his companions (hypocrites) returned (home). A party of the believers remarked that they would kill those (hypocrites) who had returned, but another party said that they would not kill them. So, this Divine Inspiration was revealed: "Then what is the matter with you that you are divided into two parties concerning the hypocrites." (4.88) The Prophet (ﷺ) said, "Medina expels the bad persons from it, as fire expels the impurities of iron."
Narrated Zaid bin Thabit:
When the Prophet (ﷺ) set out for (the battle of) Uhud, some of those who had gone out with him, returned. The companions of the Prophet (ﷺ) were divided into two groups. One group said, "We will fight them (i.e. the enemy)," and the other group said, "We will not fight them." So there came the Divine Revelation:-- '(O Muslims!) Then what is the matter within you that you are divided. Into two parties about the hypocrites? Allah has cast them back (to disbelief) Because of what they have earned.' (4.88) On that, the Prophet (ﷺ) said, "That is Taiba (i.e. the city of Medina) which clears one from one's sins as the fire expels the impurities of silver."
Narrated Zaid bin Thabit:
Regarding the Verse:-- "Then what is the matter with you that you are divided into two parties about the hypocrites?" (4.88) Some of the companions of the Prophet (ﷺ) returned from the battle of Uhud (i.e. refused to fight) whereupon the Muslims got divided into two parties; one of them was in favor of their execution and the other was not in favour of it. So there ware revealed: "Then what is the matter with you that you are divided into two parties about the hypocrites?" (4.88). Then the Prophet (ﷺ) said "It (i.e. Medina) is aTayyaboh (good), it expels impurities as the fire expels the impurities of silver."
Zaid b. Thabit reported that Allah's Messenger (ﷺ) set out for Uhud. Some of those persons who were with them came back. The Companions of Allah's Messenger (ﷺ) were divided in two groups. One group said: We would kill them, and the other one said: No, this should not be done, and it was on this occasion that this verse was revealed:" Why should you, then, be two parties in relation to hypocrites?" (iv. 88).