A Different Birth

In Isaac vocabitur tibi semen ... Promissionis enim verbum hoc est: secundum hoc tempus veniam: er erit Sarae filius. Non, ergo, inquit, per ordinem nativitatis carnalis Isaac nascitur; quippe cum jam Abraham emortui esset corporis, et mortua vulva Sarae, sed per virtutem promittentis. Merito ergo non carnis, sed Dei filius dicitur qui ex adventu et sermone Dei nascitur. Guillelmus S Theodorici Abbas, Expositio In Epistolam Ad Romanos, Liber IX Source: Migne PG 180.646a

Through Isaac your seed shall be known ... For this was the word of His promise: at this time I shall come and Sarah shall have a son. 1 Thus He says that it is not according to the carnal order of birth that Isaac shall be born, since Abraham was already barren in his body and Sarah was barren in her womb, but through the power of the promise. Rightly then he is not called a son of the flesh but of God, he who is born from the coming and the word of God. William of St Thierry, Commentary on Romans, Book 9 1 Rom 9.7-9, Gen 18.10