Musannaf Ibn Abi Shaybah

Hasan considered it permissible for a man to marry his slave to his slave-girl without dowry and without witnesses.

Hazrat Ata says that a man can marry his slave to his bondwoman without witnesses; however, if he appoints someone as a witness, it is better.

Ibrahim says that the predecessors used to compel slaves and slave-girls to marry and would close the door for them.

Hazrat Ibn Abbas (may Allah be pleased with them) says that a man can marry his slave to his bondwoman without a dowry.

Hazrat Abu Fatimah says that I asked Hazrat Ibn Sirin, "If a man says to his slave, 'Take my such-and-such slave-girl, if you wish, marry her, and if you wish, sell her and give me her price,' then what is the ruling regarding this?" He replied, "He should make her wear a dress."