Musannaf Ibn Abi Shayba 13:549

Abu Bakr narrated to us, he said: Ibn al-Mubarak narrated to us, from Yahya ibn Bishr, that he heard Ikrimah saying: "Do not purchase *gharar* (uncertainty/risk) in the form of a lost animal or a runaway slave, for you do not know—perhaps you will never find them, and your capital will be consumed unjustly."