Genesis 16 - 18

Chapter 16 ushers in one of the most sordid tales in the Bible. Abram made a mistake of historic proportions when he agreed with Sarai, his wife, to have offspring with her Egyptian servant, Hagar. The ramifications of that sin are still wreaking havoc in the world today.
Immediately after Hagar conceived a child by Abram, she began taunting Sarai, who was still barren. This was a development Sarai didn't plan and didn't like one bit. She complained to her husband, who tried to act uninvolved and told her to take care of the situation as she saw fit. So Sarai mistreated Hagar until she fled.
But Jesus sees everything. He appeared to Hagar as she sat by a well in the desert. Jesus almost always begins a conversation by asking questions, although He already knows all the answers. He asked Hagar where she had come from and where she was going. He wanted her to think about those things. When she told Him she was running away from Sarai, He instructed her to go back and submit to whatever treatment she was subjected to. Then He told her the child in her womb was a male and told her that she was to name him Ishmael, also making the prediction that he would be a man of war, living in hostility against his fellow man.
Hagar her realizes this appearance is from God and she calls Him El-Shaddai, which is Hebrew for the One who sees me. When she returned and had a son in Abram's 86th year, Abram named him Ishmael.
Chapter 17 details the second covenant God makes with Abram,the covenant of circumcision. This ritual would serve to further set Abram's tribe apart from the general populace. Here, God changed Abram's name to Abraham, meaning father of many, and Sarai became Sarah.
God told Abraham to circumcise every male on their eighth day of life, as a sign they were God's people. Modern medicine has found babies to have more resistance to bleeding from circumcision, and are less likely to remember the pain, up to and including, their eighth day. Seems God knows what He is doing.
Again, God reassures Abraham that he and Sarah will, indeed, have a son of their own. Abraham humbly questioned this assertion by God, because of his and Sarah's advanced age. Tenderly, God insists there will be an Isaac born to the couple, from whom the King would come. Abraham pleaded also for his son, Ishmael, to be blessed by God, and God promised to also make him a great nation.
Apparently, God made a habit of visiting with his friend, Abraham. Chapter 18 tells of a visit they had near Mamre one hot day. God and two other visitors came to speak with him about their plans to destroy Sodom and Gomorrah. Again, God promised a son to Abraham and Sarah and gave them an idea of when Isaac, meaning laughter, would be forthcoming, which made Sarah laugh.
When Abraham heard God's plans to destroy Sodom, he became alarmed for his nephew, Lot, who had become an important person in the city of Sodom. Abraham began bargaining with God for the life of Lot and his family. God promised to relent if only ten good people could be found in the city. Apparently, there were not ten to be found.