Musnad Ahmad 28:184

Khalaf ibn al-Walid narrated to us, Abu Ja'far—meaning al-Razi—narrated to us, from Matar al-Warraq, from 'Amr ibn Shu'ayb, from his father, from his grandfather, who said: "I saw the Prophet, may Allah bless him and grant him peace, praying in his sandals, and I saw him praying barefoot. I saw him drinking while standing, and I saw him drinking while sitting. I saw him turning away from his right, and I saw him turning away from his left."