Musnad Ahmad 937:245

'Abd al-Rahman ibn Mahdi narrated to us, Shu'bah narrated to us, from Abu 'Imran al-Jawni, from 'Abdullah ibn al-Samit, from Abu Dharr, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Aslam, may Allah keep it safe, and Ghifar, may Allah forgive it."