Musnad Ahmad 462:21

Al-Hakam ibn Nafi' narrated to us, he said: Isma'il ibn 'Ayyash narrated to us, from Buhayr ibn Sa'd, from Khalid ibn Ma'dan, from al-Miqdam ibn Ma'di Karib, that he heard the Messenger of Allah, peace and blessings of Allah be upon him, saying: "Whatever you feed yourself is a charity for you, and [likewise] your child, your wife, and your servant."