Musannaf Ibn Abi Shayba 17:380

Humaid ibn Abd al-Rahman narrated to us, from Musa ibn Ubaydah, from Imran ibn Abi Anas, from Malik ibn Aws ibn al-Hadthan, who said: Abu Dharr arrived from al-Sham and entered the mosque, and Uthman was in it. He said, "Peace be upon you." He (Uthman) said, "And upon you be peace. How are you, O Abu Dharr?" He said, "I am well. How are you, O Uthman?"