The descendants of Abraham and Sarah who migrated to Egypt at the end of the Ancestral Period remained there for about four centuries. During that time they became slaves of the Egyptians. The book of Exodus tells of their deliverance from slavery under Moses' leadership in about the year 1275. After suffering ten plagues which culminated with the slaying of the Egyptian firstborn, the king of Egypt released the Hebrews.  Moses led the people eastward but the Egyptian king changed his mind and pursued them. The Hebrew people found their way blocked by water, but the water parted, allowing them to pass through; then it surged back over the Egyptian chariots. The exodus from Egypt is the central saving act of God in the Old Testament.