Two Births

Abraham autem genuit Isaac. Qui interpretatur risus. Risus autem sanctorum est, non stulta cachinnatio labiorum, sed rationabile gaudium cordis, qui fuit per omnia mysterium Christi. Sicut enim ille Isaac, desperantibus jam parentibus, in ultima senectute donatus est laetitia suis, ut cognoscatur, quis non erat filius naturae, sed gratiae: sic et noster Isaac in novissimo fine productus est a matre Judea gaudium cunctis, sicut dicit angelus ad pastores: Ecce evangelizo vobis gaudium magnum, quod erit omni plebi. Unde ait Apostolus: Postquam venit plenitudo temporis, misit Deus Filium suum natum ex muliere, natum sub lege. Sed iste per virginem, ille de anu, ambo extra spem naturae. Ille postquam mater ejus parere posse cessaverat, iste priusquam mater ejus parere posse inciperet. Sed ille de anicula ideo deficiente, iste autem de virgine incorrupta: quia ille Isaac filios fuerat generaturus in lege corrumpenda, iste autem in gratia permansura. Opus Imperfectum in Matthaeum, Homilia I Source:  Migne PG 56.742

'For Abraham sired Isaac.' 1 Which name of Isaac is interpretated laughter. And it is the laughter is of the holy, not the foolish chuckling of lips, but the rational joy of the heart, this one who was in everything a type of Christ. For as that Isaac was given for their joy to parents already despairing in final old age that it might be known that he was not a son of nature, but of grace, so even our Isaac at the end of most recent times was brought forth in Judea for the joy of all, as the angel said to the shepherds: 'Behold, I bring to you news of great joy that shall come to all people.' 2 Whence the Apostle said: 'After came the fullness of time, God sent His own Son, born from a woman, born beneath the law.' 3 But He was from a virgin, the other from an old woman, both beyond the hope of nature. One was born after his mother had ceased to be able, the other before His mother was able. One was from an old worn out woman, the other from a virgin untouched; for Isaac was born into the law that would perish, the other into grace eternal. Opus Imperfectum on Matthew, from The The First Homily 1  Mt 1.2 2. Lk 2.10 3  Gal 4.4