Musannaf Ibn Abi Shayba 3:829

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Khalid, who said: I saw Abu Qilabah, and upon him was a *jubbah* (outer garment) and a washed *milhafah* (wrap/sheet), and he was praying while *mudtabi‘an* (having the garment under one armpit and over the opposite shoulder), having brought out his hand.