The carol’s title sets the theme: the eternal Son of God, without ceasing to be God, took on human nature and was born as Jesus of Nazareth, so that Matthew could call him “Immanuel, God with us.” That good news answers humanity’s oldest problem, the fall, in which Adam and Eve chose to determine good and evil for themselves and were cut off from God’s presence.
Paul reminds the Ephesians that they were once without Christ, strangers to the promises, far off and without hope, until the blood of Christ brought them near. What God had promised in the wilderness – “I will dwell among the children of Israel and will be their God” – is fulfilled in the incarnation, and it calls his people to a holiness set apart from the ways of the nations around them.