Musannaf Ibn Abi Shayba 3:787

Narrated to us Abd al-Salam ibn Harb, from Ishaq ibn Abd Allah, from Ibrahim ibn Abd Allah ibn Hunayn, from Ibn Abbas, from Ali ibn Abi Talib, that the Messenger of Allah (may Allah bless him and grant him peace) said: "If your lower garment (izar) is wide, then wrap it around your body (tawashah bihi). And if it is narrow, then tie it around your waist (itazir bihi)."