Abu Dawud
Zakat
Book Number: 003 / Hadith Number: 1663
Narated By Umm Bujayd : She took the oath of allegiance to the Apostle of Allah (pbuh) and said to him: Apostle of Allah, a poor man stands at my door, but I find nothing to give him. The Apostle of Allah (pbuh) said to her: If you do not find anything to give him, put something in his hand, even though it should be a burnt hoof.