A Bedouin narrated from his father that he prayed behind the Prophet (peace and blessings be upon him), and the Prophet (peace and blessings be upon him) gave the salam to the right and to the left (on both sides).
Ahmad recorded it, and its chain contains a narrator who has not been named.
Hadith Referenceمجمع الزوائد ومنبع الفوائد / كتاب الصلاة / 2875