Human sin and divine grace
The contrast between Sarai (Genesis 16) and Sarah (Genesis 17) is striking. It is the contrast between human sin and divine grace: "Don't call your wife by the name Sarai anymore. Instead, her name is Sarah (princess). I will bless her ... " (Genesis 17:15-16). What she was is a thing of the past. What she will become is the work of God's grace. The Lord intends to bless her and make her a blessing - "she will become a mother of nations and kings will come from her" (Genesis 17:16). Human experience can always be viewed from two very different perspectives - the perspective of sin and the perspective of grace. We must learn to look at our lives and say, "Sin shall not have dominion. Grace is victorious" (Romans 6:14).