Musnad Ahmad 28:151

Muhammad ibn Ja'far narrated to us, Sa'id ibn Abi 'Aruba narrated to us, from Husayn al-Mu'allim, from 'Amr ibn Shu'ayb, from his father, from his grandfather, who said: "I saw the Messenger of Allah (peace and blessings of Allah be upon him) praying, turning to his right and to his left. And I saw him praying barefoot and wearing sandals. And I saw him drinking while standing and while sitting." Muhammad—meaning Ghundar—said: Al-Husayn informed us of it, from 'Amr ibn Shu'ayb, from his father, from his grandfather.