Musnad Ahmad 788:22

Waki’ narrated to us, from Harmalah ibn Qays, from Muhammad ibn Abi Ayyub, from Abu Musa, who said: "There were two securities during the time of the Messenger of Allah, may Allah bless him and grant him peace. One of them was lifted, and the other remained: 'And Allah would not punish them while you are among them, nor will Allah punish them while they seek forgiveness' [Al-Anfal: 33]."