Let us pray (in silence) [that Christ will dwell in our hearts]
God of all hope and joy,
open our hearts in welcome,
that your Son Jesus Christ at his coming
may find in us a dwelling prepared for himself;
who lives and reigns with you and the Holy Spirit,
one God now and for ever.
NZPB p. 554
Before proceeding might I stress: I am not here writing against Advent being a season of preparation.
We too easily and quickly turn the gospel upside down so that we tidy things up to make it all right for God to come. Rather than God in God's coming makes it all right [even when it might continue to look untidy]. We seek forgiveness and reconciliation in order to make a good place for God to come to. Whereas the gospel stress is that forgiveness and reconciliation is the result of God's coming. In services we have absolution to make us pure enough prior to receiving communion - this is a new development only since the sixteenth century! The gospel message is that we all arrive at Christ's table sinners and receive the blood of Christ shed for the forgiveness of sins. It is communion that absolves us, Christ's death that reconciles us. In some services there is even verbal absolution before a baptism - rather than the gospel realisation that baptism is for the forgiveness of sins. If verbal absolution is sufficient to forgive sins - why send Jesus to die? As if action is not required for reconciliation.
The allusion in this collect holds together Christ's first advent, the current eucharistic and every-moment advent, and the advent in glory. The collect applies to us individually and as a community. The story of Christ's first advent has that there was no dwelling prepared for him. In contrast we pray that "Christ at his coming may find in us a dwelling prepared for himself." There is a strong connection with Mary - a primary focus of this Sunday - she who is the the dwelling for Christ - the Theotokos - the God-bearer. Mary in her person is the answer to this prayer.
This collect is a version of the Gelasian collect (no. 1127). In the Gregorian Sacramentary (no. 809) it was one of the "other prayers for Advent", in the Missale Gallicanum vetus (no. 40) it was the collect for the first of three Advent Masses.
The Great Advent O Antiphons 17 - 23 December
Original, Southern Hemisphere Advent collects
An outline example and resources for an Advent Eucharist
Advent in the Southern Hemisphere