Musnad Ahmad 32:1958

Muhammad ibn Ja'far narrated to us, Shu'bah narrated to us, and Hajjaj narrated to us, he said: Shu'bah narrated to me, he said: I heard Qatadah narrating from Anas ibn Malik: "That Abd al-Rahman ibn Awf married a woman for the weight of a date stone of gold, and that was permitted."