God promised Abram and Sarai a child, but when that promise was slow in coming, they decided to have Abram sleep with Sarai's maidservant Hagar instead. This was a bad decision, but God still kept his promise to Abram and Sarai, and God made the descendents of Ishmael, Hagar's child, more numerous than one could count. God is not limited by our bad decisions, and whether or not we are faithful, God's plans will come to pass.