Matthew 1:18 (BSB)

This is how the birth of Jesus Christ came about: His mother Mary was pledged in marriage to Joseph, but before they came together, she was found to be with child through the Holy Spirit.

From Matthew 1. Also in the ESV.

Commentary on Matthew 1:18

• John Calvin (Reformed), Calvin's Commentaries on Matthew 1:18: 18. Now the birth of Jesus Christ Matthew does not as yet relate the place or manner of Christ’s birth, but the way in which his heavenly generation was made known to Joseph. First, he says that Mary was found to be with child by the Holy Spirit Not that this secret work of God was generally known: but the historian mixes up, with the...
• Matthew Henry (Presbyterian), Matthew Henry's Complete Commentary on Matthew 1:18-25: The mystery of Christ's incarnation is to be adored, not pried into. If we know not the way of the Spirit in the formation of common persons, nor how the bones are formed in the womb of any one that is with child (Ecc 11:5), much less do we know how the blessed Jesus was formed in the womb of the blessed virgin.
• John Gill (Reformed Baptist), Exposition of the Old and New Testaments on Matthew 1:18: Now the birth of Jesus Christ,.... The Evangelist having finished the genealogy of Christ, proceeds to give an account of his birth, which includes both his conception and bringing forth; and which he says was on this wise, so, "after this manner", and which was very wonderful and astonishing; when as, for his mother Mary was found with child, not of man, no, not of...
• Albert Barnes (Presbyterian), Barnes' New Testament Notes on Matthew 1:18: Verse 18. On this wise. Thus. In this manner. Espoused. Betrothed, or engaged to be married. There was commonly an interval of ten or twelve months, among the Jews, between the contract of marriage and the celebration of the nuptials, see ; , yet such was the nature of this engagement, that unfaithfulness to each other was deemed adultery. See . With child of the Holy Ghost. .