Abraham marries Keturah and has six more sons. We don’t know if that was before or after the death of Sarah. This closes out the story of the life of Abraham before moving on to the life of Isaac’s sons. The birth of Isaac’s sons continues the establishment of the Nation of Israel. Ishmael’s offspring are also listed in this chapter, showing God keeping his promise to Abraham from Genesis 17:20; which is another way of closing out the life of Abraham. Since Isaac was 40 when he married and 60 when his sons were born, Rebekah and Isaac had to wait 20 years for her to become pregnant.
What is clear from this chapter is that God keeps his promises. His promise to Abraham was that he would be the father of many nations. That was fulfill through Isaac, Ismael, and his other sons. He promised that Isaac would be the father of a nation. Although it took a while, Abraham saw his grandsons live to age 15. We have many promises from God as well: our sins are forgiven, we have the Holy Spirit inside us, and we have the power to overcome sin in our lives. Like Abraham, we can depend on God’s promises, even when it doesn’t look or feel like it.