Musannaf Ibn Abi Shayba 2:151

2268. Muhammad ibn Ubayd narrated to us, from al-A’mash, from Malik ibn al-Harith, from his father, who said: We were with Abu Musa at ‘Ayn al-Tamr in the post house. He gave the adhan and the iqamah. We said to him, "How did you go out to the wilderness?" He said, "That and this are the same."