(Is it not enough for them) i.e. for the people of Mecca as a sign for your prophethood, O Muhammad, (that We have sent down unto thee the Scripture) We sent down Gabriel with the Qur'an (which is read unto them) and relating to them the commands, prohibitions and the events of past nations? (Lo! Herein) i.e. in the Qur'an (verily is mercy) that saves from chastisement, for those who believe in it, (and a reminder) an admonition (for folk who believe) in Muhammad (pbuh) and in the Qur'an.