Musnad Ahmad 30:2989

Yahya narrated to us, from Sufyan, from Muzahim ibn Zafar, from Mujahid, from Abu Hurayrah, from the Prophet (peace be upon him) — Yahya was in doubt regarding this — he said: "A dinar you spent in the way of Allah, and a dinar for the needy, and a dinar for a slave, and a dinar for your family; the greatest of them in reward is the dinar you spend on your family."