Musnad Ahmad 32:2059

Muhammad ibn Ja‘far narrated to us, Shu‘bah narrated to us, from Humayd al-Tawil, who said: I heard Anas ibn Malik saying: "The Messenger of Allah (may Allah bless him and grant him peace) called for a young boy of ours and cupped him, then he gave him his wage, a sa‘ or two sa‘s, and he spoke to his masters to lighten his tax for him."