The Birth of Jesus.
v.18-21 An angel announces (to Joseph in a dream) the conception of Jesus (see Lk 1:26-38). Jesus means “God saves” and the angel states that he will save his people from their sins (allusion to Ps 130:8).
v.22-23 Jesus is the prophesied Immanuel (Is 7:14) born of a virgin. Immanuel means “God with us.” Fulfillment of prophecy is a major theme in Matthew.
v.24-25 Joseph follows the angel’s instruction and takes Mary as his wife. They did not have sexual relations until after Jesus was born.
A fuller account of Jesus’ birth is given in Lk 1:26-2:21.

Read Matthew 1:18-25