“Now the birth of Jesus Christ was on this wise: When as his mother Mary was espoused to Joseph, before they came together, she was found with child of the Holy Ghost.”
Matthew 1:18 — Greek Interlinear
Church Fathers on Matthew 1:18
Having said above, 'And Jacob begat Joseph,' to whom Mary being espoused bare Jesus; that none who heard should suppose that His birth was as that of any of the forementioned fathers, he cuts off the thread of his narrative, saying, 'But Christ’s generation was thus.' As though he were to say, The generation of all these fathers was as I have related it; but Christ’s was not so, but as follows, 'His mother Mary being espoused.'
He announces that he is to relate the manner of the generation, shewing therein that he is about to speak some new thing; that you may not suppose when you hear mention of Mary’s husband, that Christ was born by the law of nature.
Yet it might be referred to the foregoing in this way, The generation of Christ was, as I have related, thus, 'Abraham begat Isaac.'