This verse is part of the dialogue between Allah and Prophet Musa (Moses, peace be upon him) after the Children of Israel had worshipped the calf. Musa prayed for Allah’s forgiveness and mercy, saying:
“And decree for us in this world [that which is] good and [also] in the Hereafter; indeed, we have turned back to You.”
[Allah] said, “My punishment – I afflict with it whom I will, but My mercy encompasses all things. So I will decree it [especially] for those who fear Me, give zakah, and those who believe in Our verses – those who follow the Messenger, the unlettered prophet, whom they find written [mentioned] in the Torah and the Gospel with them…”