It is narrated from Wathilah bin Asqa’ (may Allah be pleased with him) that the Prophet (ﷺ) would turn to his right and left while saying salam, until his cheeks would become visible.
Hadith Referenceمسند الإمام الشافعي / كتاب الصلاة / 261
Hadith Takhrijاسنادہ ضعیف لشدۃ ضعف شیخ الشافعی، أخرجہ البیہقی فی معرفۃ السنن والآثار: 933۔