Now the birth of Jesus Christ was as follows. When His mother Mary had been betrothed to Joseph, before they came together she was found to be with child by the Holy Spirit. And Joseph her husband, being a righteous man, and not wanting to disgrace her, desired to put her away secretly. But when he had considered this, behold, an angel of the Lord appeared to him in a dream, saying, “Joseph, son of David, do not be afraid to take Mary as your wife; for that which has been conceived in her is of the Holy Spirit. And she will bear a Son; and you shall call His name Jesus, for it is He who will save His people from their sins.” Now all this took place that what was spoken by the Lord through the prophet might be fulfilled, saying, “Behold, the virgin shall be with child, and shall bear a Son, and they shall call His name Immanuel,” which translated means, “God with us.” And Joseph arose from his sleep, and did as the angel of the Lord commanded him, and took her as his wife, and kept her a virgin until she gave birth to a Son; and he called His name Jesus. Matthew 1:18-25.
In these verses an angel (Gabriel? we don’t know) appears to Joseph to stop him from divorcing Mary. In doing so, he tells Joseph about the son Mary will bear, and that He would save His people from their sins. Matthew then tells us readers that this fulfills the words of Isaiah 7:14. Jesus is “God with us.” Joseph demonstrates his faith in the Lord in that he gets up and does what the angel commands, taking Mary as his wife.
Jesus is a Savior who delivers His people from their sin. Jesus is Immanuel: God (in the person of the eternal Son) with us.