That founding father was Abram, an obscure shepherd and the reputed son of an idol maker, who packed his tents and his family and left his ancestral homeland in upper Mesopotamia, along with its manifold deities, in obedience to the command of the one true God: "Go … from your father's house to the land I will show you. I will make of you a great nation, and I will bless you, and make your name great."
And so at the age of 75, Abram and his wife, Sarai, set out for the land of Canaan. There he would live the life of a nomad, tending his flocks, first at Shechem, a great walled city guarding a strategic pass between Mount Ebal and Mount Gerizim, and later at Bethel, Ai, Hebron, and other cities to the south.
It was at Shechem, according to the Hebrew Scriptures, that the Lord first appeared to Abram and promised that his descendants would inherit the land around him. Out of gratitude, Abram erected an altar—an act of veneration he may have learned from his forebears' worship of Nanna, the great moon god of Ur, and his son Utu, the sun god. In years to come, Abram would build many altars and offer many sacrifices to the one God he had come to believe was over all creation, a God he knew as Yahweh.
Despite God's promise that Abram would father a great nation, Sarai remained childless in her 70s. Despairing, Sarai offered Abram her handmaid, Hagar, who bore him a son. They named him Ishmael. (According to Islamic tradition, Ishmael would become the father of the Arab people.) The Lord appeared to Abram again, saying the promise would be fulfilled not through Ishmael but through a son to be born to Sarai. God changed Abram's name to Abraham, father of a multitude of nations, and Sarai's to Sarah, meaning "princess," and a year later, at the age of 90, Sarah gave birth to Isaac. As a test of Abraham's faith, God commanded him to sacrifice Isaac but stayed his hand at the last moment.
God's covenant with Abraham was passed to Isaac and to his son, Jacob, who was given the name Israel—one who wrestled with God. Jacob's 12 sons would become progenitors of the 12 tribes of Israel. Seeking refuge from famine, Jacob and his clan migrated to Egypt, where they settled in the eastern portion of the fertile Nile Delta—the biblical land of Goshen—and their descendants "multiplied and grew exceedingly strong, so that the land was filled with them." After a few generations, their fortunes turned: They were enslaved by the pharaoh, who "made their lives bitter with hard service." Through strange chance, a young Hebrew slave named Moses was adopted into the pharaoh's household and became a prince of Egypt before he fled to the wilderness after killing a guard. There God called to Moses from a burning bush and told him to go to the pharaoh "that you may bring my people, the Israelites, out of Egypt" and lead them to the Promised Land.