"She will bear a son, and you shall call his name Jesus, for he will save his people from their sins." Matt. 1:21, RSV.
Here we have a revolutionary proclamation of the Messiah's mission. Matthew had plainly set forth Jesus from the first verse of his Gospel as the Messiah and the Son of David. In the Jewish mind, both titles had political overtones. The two came together in the vision of an earthly king. David had been an illustrious conquering warrior, and first-century Jews expected their Messiah King to carry out the same program. The Messiah, or Christ, was to be a national deliverer.
For example, in the Psalms of Solomon (written in the period between the Old and New Testaments), the anointed Son of David is a king who will arise from among the people to deliver Israel from its enemies. That Davidic king would be endowed with supernatural gifts. "With a rod of iron he shall break in pieces all their substance, He shall destroy the godless nations with the word of his mouth" (Ps. of Sol. 17:24).
Israel's history had experienced three great bondages: the Egyptian, the Babylonian, and now the Roman. The first two had had political solutions, and the Jews expected the same for the third. For first-century Jews, a Messiah who did not at least deliver the nation politically could hardly be considered genuine. The Messianic hope of the Jews rested upon a king of David's line who would free them from the oppressor.
It is in that light that we need to see the revolutionary significance of Matthew 1:21. With one inspired sentence Matthew overturns the whole Jewish concept of the Messiah. The Christ, he asserts, would not save His people from their Roman overlords, but from their sins.
The fact that Jesus, as the anointed Son of David, would not deliver people from their enemies came as a terrible disappointment to the Jews of Christ's day, including the disciples. One of Jesus' most difficult tasks was to teach a people, who preferred the conquering-king model, the true nature of His Messianic kingdom.
If we look into our hearts we will probably find that we are very much like those Jews. It is much more pleasant to get rid of an enemy ("Let them have it, Lord; give them what they deserve.") than our pet vices, which are so tempting and beguiling. Yet the proclamation of Matthew 1:21 is that Jesus came to save me from my sins.