When a slave and a free man both claim a child found in the possession of the slave's wife (who is a slave), and an Arab man claims the child is his son from his Arab wife, whose claim prevails?

Primary text

If a slave and his slave wife have a child in their possession, and an Arab man claims the child is his son from his Arab wife, and the slave presents proof supporting his claim that the child is his, the child belongs to the slave according to Abu Thur and others. The claim of the Arab man is not accepted.