Musannaf Ibn Abi Shaybah

Hazrat Nafi’ narrates that I was traveling with Hazrat Abdullah bin Abi Zakariya in the region of Rome when my riding animal needed to urinate, so the animal urinated while standing, then I rejoined him. He said: Why did you not greet (with salam)? I replied: I had just separated from you. He said: Even if you had just separated from me. The companions of the Messenger of Allah (peace and blessings be upon him) used to travel, and sometimes trees would come between them and cause separation; when they would gather again, some of them would greet others with salam.