by her
Genesis 16:2
16:2 by her. In the culture of the time, it was considered so essential for a wife to give her husband an heir that, if necessary, she could have a child by proxy, as it were, through her personal maid. Note also the similar arrangement for Jacob by his wives, Leah and Rachel (Genesis 30:3,9). The famous Nuzi tablets, found in northern Syria, confirm that it was customary and legal in the nations of that time and place for a wife unable to produce children to provide her handmaid to be a surrogate wife to her husband, with any resulting child considered her own.