Exodus 21:4

If his master have given him a wife
One of his slaves, a Canaanitish woman, on purpose to beget slaves on her, since all born in his house were his own; this is supposed to be after he was come into his house, and into his service:

and she have born him sons or daughters;
as she might have born him several of the one sort, or the other, if she was given to him quickly after his servitude began:

the wife and her children shall be her master's:
she being his slave, and bought with his money, he had a right unto her, and to the children belonging to her, the birth following the belly; and being born in his house, they were also his. Jarchi here observes, that the Scripture speaks of a Canaanitish woman, for an Hebrew woman went out at the sixth year, and even before the sixth, if she produced the signs, that is, of puberty:

and he shall go out by himself;
without his wife and children: if it be objected to this law, that it is contrary to the law of marriage, which is indissoluble, but by this dissolved; it may be replied, that the servant was not obliged by it to leave his wife, unless he chose it; on complying with certain conditions after mentioned, he might continue with her; besides, she was, according to Jarchi, but his secondary wife, and not only so, the marriage was not lawful, being with a Canaanitish woman, and not agreeable to the Lord; and being also her master's slave, to whom he had a right, he could retain her if he pleased, having only given her to his servant to beget slaves on for him.