Martin Luther,
Commentary on the Epistle to the Galatians
“ The earthly Jerusalem with its ordinances and laws represents Hagar and her offspring. They are slaves to the Law, sin and death. But the heavenly Jerusalem is Sarah, the free woman. This heavenly Jerusalem is the Church, that is to say the number of all believers throughout the world, having one and the same Gospel, one and the same faith in Christ, one and the same Holy Ghost, and the same sacraments. ”
