The Messenger of Allah ﷺ used to give the salam to his right and to his left until the whiteness of his cheek could be seen, saying, "Peace be upon you and the mercy of Allah, peace be upon you and the mercy of Allah."
حدثنا علي بن محمد حدثنا يحيى بن آدم حدثنا أبو بكر بن عياش عن أبي إسحق عن صلة بن زفر
كان رسول الله ﷺ يسلم عن يمينه وعن يساره حتى يرى بياض خده السلام عليكم ورحمة الله السلام عليكم ورحمة الله
[Sahih] * Abu Ishaq narrated with "an" (indicating a possible break in the chain), previously mentioned, no. 46, and Abu Bakr bin Ayyash was previously mentioned, no. 855. The hadith has many corroborating narrations in Abu Dawud, no. 997, and elsewhere, and Busiri graded the chain hasan.