YSAAC, YSAAK. Isaac was Abraham's son, born when both he and his wife Sarah were very old. God tested Abraham by commanding that he sacrifice Isaac, and Abraham determined to obey. He took the lad, a bundle of wood for the fire, and led the way to Mount Moriah. But as he laid Isaac on the altar and raised the knife, the angel of the Lord appeared and stopped him. He showed him a ram caught in a thicket, which Abraham sacrificed instead of Isaac (Genesis 22:1-14). Isaac's two sons were Esau and Jacob, twins by his wife Rebecca. When Isaac grew old and blind, Rebecca advised Jacob, the younger twin, to dress in animal skins and to pretend to be Esau and so defraud his older brother of Isaac's blessing (Genesis 24-26).

Jacob, by the good counsel of his mother Rebecca, won Isaac's blessing, Mel 1098. Isaac, who thought it nothing to be slain, prefigures the death of Christ, ABC 169-176. [Abraham: Jacob: Rebekka]

Ysaac, the medieval Latin variant, appears initially, ABC 169; Ysaak appears in Mel 1098.