Musnad Ahmad 1:74

Ishaq ibn Sulayman narrated to us, he said: I heard al-Mughirah ibn Muslim Abu Salamah, from Farqad al-Sabakhi, from Murrah al-Tayyib, from Abu Bakr al-Siddiq, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "The one who is evil to those he possesses shall not enter Paradise." A man said: "O Messenger of Allah, did you not inform us that this nation is the nation with the most slaves and orphans?" He said: "Yes, so honor them with the honor you give your children, and feed them from what you eat." They said: "Then what benefits us in the worldly life, O Messenger of Allah?" He said: "A righteous horse that you tether to fight upon in the way of Allah, and a slave of yours who suffices you; so if he prays, he is your brother, and if he prays, he is your brother."