مُسْنَدُ أَحْمَدَ
Musnad Ahmad 3908
Musnad of Abdullah bin Mas'ood
It was narrated from 'Abdullah bin Mas'ood (رضي الله عنه) that The Messenger of Allah (ﷺ) used to say salam in his prayer to his right and to his left. (turning his face so far that) the whiteness of his cheek could be seen.
Musnad Ahmad 3933A saheeh hadeeth; this is a da'eef isnad because Ibn Lahee’a