How can we reconcile between the infallibility of prophets and the fact that they made some mistakes, e.g Moosa's killing of a man?

All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His slave and Messenger.

Prophets and messengers, may Allaah exalt their mention, are humans but Allaah made them infallible concerning some bad deeds, e.g. the bad deeds that the Jews and Christians attributed to them.

Allaah never allowed them to make mistakes concerning conveying their messages. Therefore, the revelation reached those to whom they were sent in the way Allaah wanted.

However, since prophets, may Allaah exalt their mention, are human they made minor mistakes, but Allaah guided them to repent. In this way, we can reconcile their infallibility and the mistakes they committed. Indeed Allaah Protected them from committing major sins and they never made mistakes concerning their Messages.