"The LORD also reveals to you that he will establish a house for you," announces the prophet Nathan to David. (2 Samuel 7:11b)
This house is born for us in the divine humanity of Jesus Christ. This humanity will grow and teach and heal and suffer and finally die on the Cross, drawing into himself all the suffering we have brought upon ourselves and each other with our sins.
But by the power of his divinity this sacred humanity is raised from the dead, raised into the sacraments that make a people into a Church, into the mystical Body of the Risen Christ.
"and, like living stones, let yourselves be built into a spiritual house to be a holy priesthood to offer spiritual sacrifices acceptable to God through Jesus Christ." (1 Peter, 2:5)
Baptized into the death and Resurrection of Jesus Christ and becoming his Body and Blood that we receive in the holy Eucharist, we are the spiritual house God promised to David in an everlasting covenant.
As the Body of Christ, as Church, we become the presence of Jesus, teaching, healing, reconciling, and finally accepting the Cross with the faith that the divine humanity of Christ has blazed a trail through our suffering to the new life of the Resurrection.
So his birth is our rebirth as the resurrected humanity that is his mystical Body.