Musnad Ahmad 30:3042

Waki’ narrated to us, al-A’mash narrated to us, from Abu Salih, from Abu Hurairah, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The best charity is that which is given from what remains after sufficiency. The upper hand is better than the lower hand, and begin with those whom you support."