Sunan an-Nasa'i 1325
سنن النسائي#1325SahihAbdullah bin Mas'ud narrated that:The Messenger of Allah (ﷺ) used to say salam to his right:As-salamu 'alaykum wa rahmatullah (peace be upon you and the mercy of Allah) , until the whiteness of his right cheek could be seen, and to his left: As-salamu 'alaykum wa rahmatullah (peace be upon you and the mercy of Allah) until the whiteness of his left cheek could be seen
Scholarly Authentication
We show the most cautious grade (weakest-wins) as the overall label. Individual scholars graded it as follows:
Abu GhuddahSahih
Al-AlbaniSahih
Zubair Ali ZaiSahih
In-book reference: 13:147