20 As he considered this, an angel of the Lord appeared to him in a dream. "Joseph, son of David," the angel said, "do not be afraid to take Mary as your wife. For the child within her was conceived by the Holy Spirit. 21 And she will have a son, and you are to name him Jesus, for he will save his people from their sins." 22 All of this occurred to fulfill the Lord's message through his prophet: 23 "Look! The virgin will conceive a child! She will give birth to a son, and they will call him Immanuel, which means 'God is with us.'" 24 When Joseph woke up, he did as the angel of the Lord commanded and took Mary as his wife.
Matthew Henry's Commentary on Matthew 1:20-24
Commentary on Matthew 1:18-25
(Read Matthew 1:18-25)
Let us look to the circumstances under which the Son of God entered into this lower world, till we learn to despise the vain honours of this world, when compared with piety and holiness. The mystery of Christ's becoming man is to be adored, not curiously inquired into. It was so ordered that Christ should partake of our nature, yet that he should be pure from the defilement of original sin, which has been communicated to all the race of Adam. Observe, it is the thoughtful, not the unthinking, whom God will guide. God's time to come with instruction to his people, is when they are at a loss. Divine comforts most delight the soul when under the pressure of perplexed thoughts. Joseph is told that Mary should bring forth the Saviour of the world. He was to call his name Jesus, a Saviour. Jesus is the same name with Joshua. And the reason of that name is clear, for those whom Christ saves, he saves from their sins; from the guilt of sin by the merit of his death, and from the power of sin by the Spirit of his grace. In saving them from sin, he saves them from wrath and the curse, and all misery, here and hereafter. Christ came to save his people, not in their sins, but from their sins; and so to redeem them from among men, to himself, who is separate from sinners. Joseph did as the angel of the Lord had bidden him, speedily, without delay, and cheerfully, without dispute. By applying the general rules of the written word, we should in all the steps of our lives, particularly the great turns of them, take direction from God, and we shall find this safe and comfortable.