It is narrated from Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) would give the salam to his right: "As-salamu alaykum wa rahmatullah (Peace be upon you and the mercy of Allah)", and likewise to his left, until the side of his face became visible to the people.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 10144