Musnad Ahmad 25:933

Surayj and Yunus narrated to us, they said: Hammad—meaning Ibn Salamah—narrated to us, from Abdullah ibn Uthman, from Sa’id ibn Jubayr, from Ibn Abbas: That the Messenger of Allah (peace and blessings of Allah be upon him) and his companions performed Umrah from Ji’ranah, and they practiced *idtiba’* (placing the middle of the garment under the right armpit and the ends over the left shoulder) with their cloaks under their armpits. Yunus narrated to us: "They placed their cloaks," and Yunus said: "And they threw them over their left shoulders."