Son of the aged Sarah and Abraham; born in accordance with the promise to Abraham of an eternal covenant (Gen. 17: 15–21). Abraham's faith was put to the test when he was ordered to sacrifice this instrument of the promise. In surviving the test by his obedience, Abraham recognized that God's promise was a sheer gift, not something to be possessed by legal entitlement. Isaac was spared at the last moment of the intended sacrifice by divine intervention, and a ram substituted for the lad. Some expositors have interpreted the narrative as a tale to define Israel's repudiation of pagan child sacrifice or as a stage in the evolution of religion. Paul treats the remarkable birth of Isaac in fulfilment of God's promise as paralleled by the choosing of the Galatians as children of the promise; it is given to those who have faith, without regard to their physical descent (Gal. 4: 28). The epistle to the Hebrews (11: 19) hints at the release of Isaac for the sacrifice as a ‘type’ of the resurrection of Christ, but it is not until the so-called epistle of Barnabas 7 at the end of the 1st cent. (and not in the NT) that the sacrifice of Isaac is used to prefigure Jesus' sacrifice on the cross. It then became a theme for many great artists, as in a mosaic of the 6th cent. in Ravenna. In Judaism the sacrifice of Isaac, called the aqedah (‘binding’), almost paralleled the significance of the crucifixion of Jesus in Christianity.