Abraham, also called the first Hebrew, is thought to have lived sometime around 2,000 BC, and was known for leaving his home of Ur to go to Haran when God called him. The Bible tells the story of his travels from Ur to Haran, through Canaan, into Egypt and back to Haran.
Abraham was married to Sarah, who was barren. God promised to give him a son through whom a mighty nation would arise. Having a son seemed impossible due to the old age of Sarah, which led to Abraham doubting God's promise at one time and trying to have a child with his servant girl, Hagar. This led to Abraham suffering for that sin. His son from Hagar, Ishmael, turned against the son from Sarah, Isaac, which meant that Ishmael had to leave Abraham's household. Isaac was born when Abraham was 100 and Sarah was 90.
Another part of Abraham's life includes God telling him to offer his son Isaac as a burnt offering to prove his faith. Abraham obeyed this command, bringing Isaac to Mount Moriah and laying him on the alter. At the last moment, God told Abraham not to kill Isaac and gave him a ram.
Abraham also asked God to spare the cities Sodom and Gomorrah because his nephew Lot lived there. God sent an angel to save Lot and his family but destroyed the cities because of their abominations.
God established His covenant with Abraham, and the seal and reminder of the covenant was circumcision. All of Abraham's male descendants would be circumcised as a reminder of God's promises to Abraham.