1 Now Sarai Abram’s wife bare him no children: and she had an handmaid, an Egyptian, whose name was Hagar. 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. 3 And Sarai Abram’s wife took Hagar her maid the Egyptian, after Abram had dwelt ten years in the land of Canaan, and gave her to her husband Abram to be his wife.
The Biblical record comes from a very different culture than the one we have today, especially the Old Testament portion of it. A wife giving a servant to be a second wife to her husband is entirely incompatible with today’s social norms for a number of reasons.
While morals are constant, challenges and priorities do change, and with them our measure of what is socially acceptable behavior. I don’t think any of us can fully empathize with what it was like to live in the time and place of Abram and Sarai, and thus we are not equipped to judge their behavior. If they genuinely felt that they were being moral, then that is enough. Nor do we need to apologize for following a different behavior today. If we genuinely believe that we are moral, then that is enough.
I do think that there is something admirable to how Abram and Sarai are trying to do their part to make God’s promise a reality. This effort of theirs is ultimately not the fulfillment that the Lord has in mind, He intends to perform a miracle on their behalf just a little down the road. But they don’t know that yet, and so they are faithfully trying to help out how they can.