Abbas bin Sahl al-Sa'idi narrates that he was in a gathering in which his father Sayyiduna Sahl (may Allah be pleased with him), Sayyiduna Abu Hurayrah, Sayyiduna Abu Usayd and Sayyiduna Abu Humayd (may Allah be pleased with them) were present. They discussed the prayer of the Messenger of Allah (peace and blessings be upon him), and they mentioned that he (peace and blessings be upon him) used to give the salam to his right and to his left.
Hadith Referenceالمعجم الكبير للطبراني / باب السين / 5717