Musnad Abu Ya'la al-Mawsili 115:95

'Amr Muhammad al-Naqid narrated to us, Sulayman ibn 'Ubayd Allah Abu Ayyub al-Raqqi narrated to us, 'Ubayd Allah ibn 'Amr al-Raqqi narrated to us, from Ma'mar, from Qatadah, from Anas ibn Malik, who said: The Messenger of Allah (may Allah bless him and grant him peace) forbade that a man should put on his sandals while standing.