God is faithful to fulfill His promises, even though our faith and obedience sometimes waver. In Genesis 20, Abraham, after traveling south, repeats a sin from earlier in his life - fear about his personal safety leading him to say that Sarah is his sister instead of his wife. It is graciously followed by the first section in chapter 21, which shows God's faithfulness in fulfilling His promise of a son born to Sarah and Abraham. The two passages, back-to-back in the Scripture, form a reminder that believers can fall into the same sins, sometimes called "besetting sins", which cause us embarrassment and regret, but our Lord and Savior is always faithful to His purposes in conforming us to be like Jesus. The apostle Paul expressed the same idea in 2 Timothy 2:13, writing, "If we are faithless, He remains faithful, for He cannot deny Himself."