After a person has run ahead of God, and made a mess, they can become either very bitter or very ready to listen. 13 years have passed since Genesis 16:18. Abram is now 99 years old, Ishmael is 13 years old, Sarai is 89, and God chooses to reaffirm his promises.  Notice that the promises of God all depend heavily on God’s faithfulness, not on Abram’s performance.