Musannaf Ibn Abi Shayba 16:588

Abu Bakr narrated to us, he said: Abu al-Ahwas narrated to us, from Abu Ishaq, from Muslim ibn Nadhir, from Hudhayfah, who said: The Messenger of Allah (may Allah bless him and grant him peace) took hold of the lower part of my calf muscle—or his calf—and said: "This is the place for the lower garment (izar). If you refuse, then lower; if you refuse, then lower; and if you refuse, then there is no right for the lower garment in the ankles."