Sayyiduna Abdullah bin Mas'ud (may Allah be pleased with him) says: "I used to see the whiteness of both cheeks of the Messenger of Allah (peace and blessings be upon him) when he (peace and blessings be upon him) gave the salam to his right and to his left."
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 9943