Musnad Ahmad 937:234

Ali ibn Ayyash and Isam ibn Khalid narrated to us, they said: Abd al-Rahman ibn Thawban narrated to us, from his father, from Makhul, from Umar ibn Nu’aym, from Usamah ibn Salman—and Isam said: Umar ibn Nu’aym al-Ansi—that Abu Dharr narrated to them, and they both said: "O Messenger of Allah, and what is the falling of the veil?" That the Prophet, peace and blessings of Allah be upon him, said: "Indeed, Allah forgives His servant," and they mentioned the like of it.