Musnad Abu Ya'la al-Mawsili 42:229

Abu Khaythama narrated to us, Waki' narrated to us, Ibn Abi Layla narrated to us, from 'Atiyya, from Abu Sa'id, who said: The Messenger of Allah (peace be upon him) said: "Charity is not lawful for a wealthy person, except for three: a warrior in the way of Allah, a wayfarer, or a man who had a neighbor and he gave him charity, so he (the neighbor) gifted it to him."