1:18–25 Matthew’s account describes more than a birth. The word translated “birth” in verse 18 could be translated “origin,” since Matthew’s account of the incarnation stresses the virgin conception of Jesus more than his birth (v. 18). The church traditionally speaks of a virgin birth, but the Gospels stress Jesus’ miraculous conception. Matthew does not say the birth itself is unusual.44 He does say the Spirit places life in Mary’s womb (v. 18).

Mary and Joseph are betrothed when Matthew’s narrative begins. Joseph has not known Mary, so when she is “found to be with child,” it seems to Joseph that Mary has betrayed him. This gives him the right to end the betrothal, which is so binding that Matthew calls Joseph “her husband,” and the termination would amount to a divorce (vv. 18–19). Because Joseph is just, he will not marry an apparently immoral woman. R. T. France explains that “just” means most basically “law-abiding” in that culture; the law was understood to require the termination of an engagement in cases of adultery.45 Because he is also merciful, Joseph plans to divorce her “quietly” instead of exposing her to public disgrace (v. 19).

God dispatches an angel to redirect Joseph. Using a dream (see also 2:12, 13, 19, 22), the angel calls him “Joseph, son of David.” Israel had endured a string of evil and feckless kings before collapsing and having no king for centuries. By Joseph’s day, David’s line is exhausted, nearly invisible. Jesus’ birth reignites hope, for he is from the line of David, but not the flesh of David. Ordinary flesh cannot save. God must and does, by renewing the kingly line himself, through his sinless Son.

“Son of David” links the virgin conception to the Davidic genealogy and Joseph’s place in it. He should “not fear to take Mary” as his wife (1:20), because her child has been conceived not by a man but by God’s Spirit. Since she is faithful, divorce is precluded. Because Joseph will adopt him, Jesus will grow up with godly parents.

The Lord often uses names to reveal his purposes (cf. Gen. 17:1–7; 32:22–28), and does so here. God chooses Jesus’ names, fulfills prophecies, and orchestrates everything. Joseph must name the infant Jesus, meaning “Yahweh saves,” because “he will save his people from their sins” (Matt. 1:21). The rest of Matthew explains how this salvation will occur.

God also ensures the fulfillment of Isaiah 7, where the prophet declared that a “‘virgin shall conceive . . . and they shall call his name Immanuel’ (which means, God with us)” (Matt. 1:22–23). Moreover, everything “took place to fulfill what the Lord had spoken by,” or “through,” the prophet (v. 22). That is, Isaiah spoke as God directed (2 Pet. 1:21) so that Isaiah’s words were both his words and God’s as they prepared the way for his salvation.

The incarnation declares that God is with us. The prototype of the Immanuel principle occurred during the reign of King Ahaz of Judah. Early in Ahaz’s reign, two adjacent kings, Pekah of Israel and Rezin of Aram, marched on Jerusalem, and Ahaz and the people shook with fear (Isa. 7:1–2). Although Ahaz was unfaithful, God sent Isaiah to declare that the invasion would fail. Since Isaiah knew Ahaz’s mind, Isaiah offered him a sign of God’s deliverance (Isa. 7:3–11). But Ahaz wanted no sign from God. He had his own plan—an appeal to mighty Assyria—and wanted no divine aid. Unwilling to admit this, Ahaz feigned piety, saying, “I will not put the Lord to the test” (Isa. 7:12). Indeed, no one should test God, but Isaiah saw through the subterfuge. He told Ahaz that he would receive a sign whether he liked it or not. “The virgin shall conceive and bear a son, and shall call his name Immanuel” (Isa. 7:14). Before this child knew right from wrong, the kings attacking Ahaz would be destroyed by Assyria, but afterward Assyria would sweep over Israel, out of control (Isa. 7:16–19; 8:4–8). Ahaz had a choice. The Immanuel principle would hold either way: if Ahaz rejected God’s presence to bless, God would still be present to curse. The Lord is always Immanuel. He offers deliverance, but if any reject him, he brings woe.

When the angel finishes speaking, Joseph wakes, believes, and obeys. He takes Mary as his wife (Matt. 1:24). Thus Joseph, like Mary, becomes God’s servant. To highlight the supernatural conception of Jesus, Matthew says that Joseph does not “know” Mary sexually until she gives birth. The “until” implies that they have normal marital intimacy afterward. Finally, Joseph names his son “Jesus,” as the angel had commanded (v. 25).