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. He may, indeed, hide himself, and remain silent; but, when our patience has been subjected to the trial, he will aid us at the time which his own wisdom has selected. How slow or late soever his assistance may be thought to be, it is for our advantage that it is thus delayed.

The angel of the Lord appeared to him in a dream This is one of two ordinary kinds of revelations mentioned in the book of Numbers, where the Lord thus speaks:

“If there be a prophet among you, I the Lord will make myself known unto him in a vision, and will speak unto him in a dream. My servant Moses is not so. With him will I speak mouth to mouth, even apparently, and not in dark speechess,”
(Numbers 12:6.)

But we must understand that dreams of this sort differ widely from natural dreams; for they have a character of certainty engraven on them, and are impressed with a divine seal, so that there is not the slightest doubt of their truth. The dreams which men commonly have, arise either from the thoughts of the day, or from their natural temperament, or from bodily indisposition, or from similar causes: while the dreams which come from God are accompanied by the testimony of the Spirit, which puts beyond a doubt that it is God who speaks.

Son of David, fear not This exhortation shows, that Joseph was perplexed with the fear of sharing in the criminality of his wife, by enduring her adultery. The angel removes his suspicion of guilt, with the view of enabling him to dwell with his wife with a safe conscience. The appellation, Son of David, was employed on the present occasion, in order to elevate his mind to that lofty mystery; for he belonged to that family, and was one of the surviving few, (102) from whom the salvation promised to the world could proceed. When he heard the name of David, from whom he was descended, Joseph ought to have remembered that remarkable promise of God which related to the establishment of the kingdom, so as to acknowledge that there was nothing new in what was now told him. The predictions of the prophets were, in effect, brought forward by the angel, to prepare the mind of Joseph for receiving the present favor.