Abraham was the patriarch and founder of the Jewish nation. In the Bible, God visited Abraham when he was 75 years old, promising him that he would be the father of a nation even though at the time he had no children.
Trusting in that promise, Abraham took his wife to the land of Canaan, becoming a prosperous shepherd. Over the years, Abraham and his wife Sarah questioned the earlier promise, and Sarah gave her Egyptian handmaiden Hagar to Abraham to father a child with. Ishmael, the resulting son, was Abraham's firstborn. When Abraham was 99, God rebuked him for Ishmael and told him that the following year Sarah would have a child, Isaac, the one that had been promised. Abraham's subsequent willingness to sacrifice Isaac to God is said to be the greatest act of faith in the Bible.