It is reported from the Prophet ﷺ that he would give the salam to his right and to his left, saying, "Peace be upon you and the mercy of Allah, peace be upon you and the mercy of Allah," until the whiteness of his cheek could be seen.Abdul-Rahman said, "Until we could see the whiteness of his cheek from this side and see the whiteness of his cheek from that side."
حدثنا وكيع وعبد الرحمن قالا حدثنا سفيان عن أبي إسحاق عن أبي الأحوص
عن النبي ﷺ أنه كان يسلم عن يمينه وعن يساره السلام عليكم ورحمة الله السلام عليكم ورحمة الله حتى يرى بياض خده وقال عبد الرحمن حتى نرى بياض خده من هاهنا ونرى بياض خده من هاهنا
Its isnad is sahih. It is a repetition of 4172, see also 4239. In ح, it reads, "Abdul-Rahman said, until he sees and sees," with the word "white" omitted the second time, and we have adopted what is in ك.