Matthew 1: 18-25 explains the divine-human origins of Jesus; Jesus as the Son of God and as Son of David. We notice that Matthew, unlike Luke, does not emphasize the virginity of Mary, and the virginal conception itself is seen as the fulfilment of prophecy (Mt 1: 22-23). Here we have the first of the Matthean “formula quotations.” The formula is the evangelist’s comment on the event described which he perceives as meant to fulfil prophecy. The Old Testament text quoted here is Isaiah 7: 14. The prophet Isaiah spoke about a ‘young woman’ who would conceive. But Matthew uses the Greek translation of the Old Testament (the LXX) which has “a virgin shall conceive…” in Isaiah 7: 14. In this Isaian text, Matthew (and indeed the early Christian tradition) recognized the scriptural support for the belief in the virginal conception and in Jesus’ divine son ship. Jesus is spoken of as “Emmanuel,” which means “God with us.” For Matthew, Jesus is the risen Lord abiding in the Church, and therefore the name Emmanuel fits well with Matthew’s presentation of Jesus in his gospel. In fact, Matthew also terminates his gospel with a similar thought of the presence of Jesus with his disciples (Mt 28: 20).
In Matthew 1: 24, the evangelist resumes his narrative. We are told that Joseph (being a just man) did exactly as he was commanded. In the following verse the evangelist says, “He knew her not until she had borne a son.” It simply means that Joseph had no conjugal relations with her until… Does it mean that Joseph had sexual relations with Mary after the birth of Jesus? If so, what about the doctrine of Mary’s perpetual virginity? The construction in Matthew 1: 25 is with ‘until’ preceded by a negative particle as in the example: “it did not rain until the end of the end of the game.” In English such a sentence would imply that it rained after the end of the game. But this is not so in Hebrew and Greek. In these languages such as negation (not…until) does not mean at all that the situation has changed or is different after the limit of the ‘until’ was reached. This is how we should understand Matthew 1: 25 too. It does not mean at all that after the birth of Jesus, Joseph ‘knew’ Mary. The time after the birth of Jesus is not just considered. At any rate Matthew’s main concern here in verse 25 is not the virginity of Mary but the obedience of Joseph in fulfilling the role assigned to him by the Lord. He named the child Jesus, a name which had been chosen by God himself (Mt 1: 21).