Musannaf Ibn Abi Shayba 19:457

Abu Bakr narrated to us, he said: Humayd ibn Abd al-Rahman narrated to us, from Hasan, from Layth, from Tawus: Regarding the slave girl who is owned by two men, and one of them has intercourse with her, he said: "Upon him is the *'aqr* (compensation for intercourse) according to the share."