Matthew 1:20 (BSB)

But after he had pondered these things, an angel of the Lord appeared to him in a dream and said, “Joseph, son of David, do not be afraid to embrace Mary as your wife, for the One conceived in her is from the Holy Spirit.

From Matthew 1. Also in the ESV.

Commentary on Matthew 1:20

• John Calvin (Reformed), Calvin's Commentaries on Matthew 1:20: 20. And while he was considering these things We see here how seasonably, and, as we would say, at the very point, the Lord usually aids his people. Hence too we infer that, when he appears not to observe our cares and distresses, we are still under his eye.
• 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 1:20: But while he thought on these things,.... While he was revolving them in his mind, considering what was most fit and proper to be done, whether to dismiss her publicly or privately; while he was consulting within himself the glory of God, the peace of his own conscience, and the credit of Mary, behold the Angel of the Lord appeared to him in a dream...
• Albert Barnes (Presbyterian), Barnes' New Testament Notes on Matthew 1:20: Verse 20. He thought on these things. He did not act hastily. He did not take the course which the law would have permitted him to do, if he had been hasty, violent, or unjust. It was a case deeply affecting his happiness, his character, and the reputation and character of his chosen companion. God will guide the thoughtful and the anxious.