Musnad Ahmad 8:125

Yahya narrated to us, Muhammad ibn ‘Amr narrated to us, Mus‘ab ibn Thabit narrated to me, from Isma‘il ibn Muhammad ibn Sa‘d, from ‘Amir ibn Sa‘d, from his father Sa‘d ibn Malik, who said: "The Prophet, may Allah bless him and grant him peace, used to perform the taslim to his right and to his left, until the whiteness of his cheeks could be seen."