Mt 1:21-23, Gen 3:15
In the Old Testament, Isaiah prophesied that our enemies would be destroyed because God was with us. (Isa 8:8-10)
Isa 8:8 And he shall pass through Judah; he shall overflow and go over, he shall reach even to the neck; and the stretching out of his wings shall fill the breadth of thy land, O Immanuel. 9 Associate yourselves, O ye people, and ye shall be broken in pieces; and give ear, all ye of far countries: gird yourselves, and ye shall be broken in pieces; gird yourselves, and ye shall be broken in pieces. 10 Take counsel together, and it shall come to nought; speak the word, and it shall not stand: for God is with us.
In the Old Testament, God spoke of destroying our enemies through the offspring of women. (Genesis 3:15)
Genesis 3:15 And I will put enmity between thee and the woman, and between thy seed and her seed; it shall bruise thy head, and thou shalt bruise his heel.
Jesus is Emmanuel. In other words, through Jesus we can be together with God. Jesus has saved us from our sins and from our enemies. (Matthew 1:21-23)
Matthew 1:21 And she shall bring forth a son, and thou shalt call his name Jesus: for he shall save his people from their sins. 22 Now all this was done, that it might be fulfilled which was spoken of the Lord by the prophet, saying, 23 Behold, a virgin shall be with child, and shall bring forth a son, and they shall call his name Emmanuel, which being interpreted is, God with us.