Musnad Ahmad 32:1816

Hassan ibn al-Rabi' narrated to us, Hammad ibn Zayd narrated to us, from al-Mu'alla ibn Ziyad, from Anas ibn Malik, who said: The Messenger of Allah (peace and blessings of Allah be upon him) said: "Whoever prays the Asr prayer, then sits dictating good until he reaches the evening, it is better than freeing eight of the children of Ishmael."