Sayyiduna Talq bin Ali (may Allah be pleased with him) said: "When the Prophet of Allah (peace and blessings be upon him) gave the salam in the prayer, we would see the whiteness of his (peace and blessings be upon him) right cheek and the whiteness of his left cheek."
Hadith Referenceالمعجم الكبير للطبراني / باب الطاء / 8215