Musnad Ahmad 980:12

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, from Sulayman, from Ibrahim al-Taymi, from his father, from Abu Mas'ud, that he was beating a slave of his. The Prophet, peace and blessings of Allah be upon him, said to him: "By Allah, Allah is more capable over you than you are over him." He said: "O Prophet of Allah, I have freed him for the sake of Allah, the Almighty and Majestic."