Musnad Ahmad 28:12

Al-Walid narrated to us, Al-Awza'i narrated to us, Hassan bin 'Atiyyah narrated to me, Abu Kabshah as-Saluli narrated to us, that Abdullah bin 'Amr bin al-'As narrated to him, saying: I heard the Messenger of Allah, peace and blessings of Allah be upon him, say: "There are forty good deeds, the highest of which is the lending of a milking goat. No servant—or he said, 'man'—performs one of these deeds, hoping for its reward or believing in its promise, except that Allah will cause him to enter Paradise because of it."