But as he considered these things, behold, an angel of the Lord appeared to him in a dream, saying, “Joseph, son of David, do not fear to take Mary as your wife, for that which is conceived in her is from the Holy Spirit.
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.
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.
Commenting on Matthew 1:18-25
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...