Musannaf Ibn Abi Shayba 9:958

Sahl ibn Yusuf narrated to us, from ‘Amr, from al-Hasan, regarding a slave who married without the permission of his master and gave a dowry: He said: If he had consummated the marriage with her, then the dowry belongs to her. And if he had not consummated the marriage with her, the master takes the dowry.