'Behold, the virgin shall be with child, and bear a Son, and they shall call His
name Immanuel,' which is translated, 'God with us.' Matthew 1:23
The name Immanuel (‘God with us’) occurs in Isaiah (7:14; 8:8) and in Matthew 1:23. In Isaiah 7:14, the prophet declared that a virgin would give birth to a son as a sign. The child’s name would be Immanuel. The child was to be a sign that God would be with King Ahaz of Judah in defence of the invading Assyrians. God had promised to be with Israelites in the Old Testament on numerous occasions. For example, He was with Joshua as Israel entered the Promised Land: ‘As I was with Moses, so I will be with you. I will not leave you nor forsake you’ (Joshua 1:5). But when it came time for Jesus to enter the world, ‘God with us’ took on a new reality. Matthew showed how the prophecy in Isaiah 7:14 had a more far-reaching meaning. The Son born to the virgin, Mary, would be God incarnate—God in the flesh, God in human form (Philippians 2:6-8).
The implications of the Incarnation are life changing. By the Holy Spirit, Jesus Christ is with you at this moment—and for all your days. By the light of the gospel we see [God] as Emmanuel, God with us.
Matthew Henry