No, Sarah was not wrong to give Hagar to Abraham. She did this because she was already very aged and naturally there was no way that she could have any children. The biblical commentators laud Sarah's decision and see her act as a very selfless one. She was concerned with having progeny, and therefore was willing to forego her own honor or exclusivity as Abraham's only wife.

Sarah's plan was to raise Ishmael as her own son, teaching him the ways of Torah.

But G‑d had another plan in mind. He wanted Abraham and Sarah to have their own child...and so Sarah, miraculously, at the age of ninety, gave birth to Isaac, the second forefather of the Jewish people!

Chana Weisberg for