God had promised Abraham that he would birth a nation that would bless the world (Genesis 12:1-4). This required a son, but no heir had come (Genesis 15:1-15). And it had been so long since the promise. Finally, when Abraham was 99 years old (and Sarah 90), the Lord appeared again, once more promising a child to Abraham. Sarah laughed (Genesis 18:12). It was funny—an old man and woman having a baby boy? The joy and the laughter arrived when God’s promise came true, when Isaac was born (Genesis 21:5).