Charles Ellicott Commentary Matthew 1:20

"But when he thought on these things, behold, an angel of the Lord appeared unto him in a dream, saying, Joseph, thou son of David, fear not to take unto thee Mary thy wife: for that which is conceived in her is of the Holy Spirit." — Matthew 1:20 (ASV)

While he thought on these things — The words imply a conflict, a perplexity; and the words of the angel came as the solution to his doubts.

In a dream — From the Jewish point of view, dreams were the received channels of divine communication to the aged, and open visions in a state of ecstasy to the young (Joel 2:28). This, at least, falls in with what has been inferred about Joseph’s age.

Joseph, you son of David — The latter words were, in the highest degree, significant. His character as the heir of Messianic hopes, which was indeed at the root of his fears, was fully recognized. What he was commanded to do would not be inconsistent with that character and would bring about the fulfillment of those hopes.

Your wife — Here again, stress is laid on the fact that Mary was already entitled to that name and had done nothing to forfeit it.

Conceived — Better, perhaps, begotten.