Musannaf Ibn Abi Shayba 36:222

Zayd ibn al-Hubab narrated to us, he said: Muhammad ibn Salih narrated to me, he said: Yazid ibn Zayd, the freed slave of Abu Usayd al-Badri, narrated to me, from Abu Usayd, who said: I was with the Messenger of Allah (peace and blessings of Allah be upon him) at the grave of Hamzah. The striped garment was stretched over his head, but his feet became exposed. So, I pulled it over his feet, but his head became exposed. The Messenger of Allah (peace and blessings of Allah be upon him) said: "Stretch it over his head, and place harmal (wild rue) plants over his feet."