Genesis 16 - Sarai pushes Abram father a child with Hagar, though a lapse of faith in Abram, it would still work out to fulfill God's plan. Sarai treated Hagar with contempt but the Angel of the Lord encouraged Hagar to remain with Sarai. Her son was born and Abram called him Ishmael.
Genesis 17 - God changed Abram's name to Abraham (Father of Many). Sarai's name was changed to Sarah (Princess). God renewed His promise of the land belonging to Abraham's descendants and then promised that Sarah would have a son who would be called Isaac (Laughter).
Genesis 18 - God and two angels visit with Abraham and promise that the next year Sarah would give birth to a son. After God tells Abraham He will examine Sodom and Gomorrah, Abraham pleads for God to hold back judgment if at least 10 righteous people were in those cities.