Ishmael was the son of the slave woman, Hagar. She was Sarah's servant (see Genesis 16:15). Sarah gave Hagar to Abraham, trying to get the heir God promised through human efforts (see Genesis 16:1–4). Isaac, Sarah's son, was born to the free woman (see Genesis 21:2–3). God did something miraculous to help Sarah have this baby. This fulfilled God's promise (see Genesis 17:15–21).