Musnad Abu Ya'la al-Mawsili 109:235

Abu Khaythama narrated to us, Rawh narrated to us, Zakariya ibn Ishaq narrated to us, Abu al-Zubayr narrated to us, from Jabir, that the Messenger of Allah (peace and blessings of Allah be upon him) said: "If one of you is in charge of his brother, let him improve his shroud."