She reckons the children of her bond-woman (as Hagar was, Galatians 4:22) would be accounted her children. See Genesis 30:3 Exodus 21:4 2 Samuel 21:8 Esther 2:7. Abram hearkened to the voice of Sarai; supposing that God would accomplish his promise of a seed to come out of his loins by this way; and knowing that Sarai was not yet mentioned in the promise, as the person by whom he should have that seed; and not consulting with God, which he should have done.
Related Commentaries of Genesis 16:2
Genesis 16:2
2 And Sarai said unto Abram, Behold now, the LORD hath restrained me from bearing: I pray thee, go in unto my maid; it may be that I may obtain children by her. And Abram hearkened to the voice of Sarai.