Musnad Ahmad 30:1431

'Affan narrated to us, Hammad ibn Salamah narrated to us, 'Asal ibn Sufyan al-Tamimi informed us, from 'Ata', from Abu Hurayrah: "That the Messenger of Allah (peace and blessings of Allah be upon him) forbade al-sadl (letting one's garment hang down) in prayer."