Sunan Ibn Majah, Book 5, Hadith 969 (In-Book) ⓘ
It was narrated that ‘Ammar bin Yasir said: “The Messenger of Allah used to say the Salam to his right and to his left, until the whiteness of his cheek could be seen (saying): ‘As-salamu ‘alaikum wa rahmatullah, as-salamu ‘alaikum wa rahmatullah.’”
حَدَّثَنَا عَلِيُّ بْنُ مُحَمَّدٍ، حَدَّثَنَا يَحْيَى بْنُ آدَمَ، حَدَّثَنَا أَبُو بَكْرِ بْنُ عَيَّاشٍ، عَنْ أَبِي إِسْحَاقَ، عَنْ صِلَةَ بْنِ زُفَرَ، عَنْ عَمَّارِ بْنِ يَاسِرٍ، قَالَ كَانَ رَسُولُ اللَّهِ ـ صلى الله عليه وسلم ـ يُسَلِّمُ عَنْ يَمِينِهِ وَعَنْ يَسَارِهِ حَتَّى يُرَى بَيَاضُ خَدِّهِ " السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ . السَّلاَمُ عَلَيْكُمْ وَرَحْمَةُ اللَّهِ " .
also referenced under: Hadith 916 (Reference) & Volume 2, Book 5, Hadith 916 (DarusSalam)