Sahih Muslim
The Book of Zakat (Kitab Al-Zakat)
Book Number: 005 / Hadith Number: 2181
Abu Huraira reported Allah's Messenger (may peace be upon him) as saying: Of the dinar you spend as a contribution in Allah's path, or to set free a slave, or as a sadaqa given to a needy, or to support your family, the one yielding the greatest reward is that which you spent on your family.