Let us pray (in silence) [that our baptism might bring us unity - individually and as a community]
you have given us one baptism
for the remission of sins;
grant that we who are born of water and the Spirit
and made members of Christ,
may be one in inward faith and outward service;
through Jesus Christ our Lord
who is alive with with you and the Holy Spirit,
one God now and for ever.
NZPB p. 618c
The obvious focus of this collect is on the common-unity in baptism. People sometimes talk loosely about being baptised Anglican, or Roman Catholic, or whatever. This is incorrect. There is only one baptism. Just as there is only one, holy, catholic, and apostolic church into which each is baptised. You can buy your iPod at Noel Leeming, or the Warehouse, or Dick Smith - it is exactly the same iPod. You can get baptised in a Presbyterian building, or a Methodist building, or on a beach - it is exactly the same baptism. God has given us only one baptism.
There is another slant to the unity in the collect. Each person's unity between what is "inward" and what is "outward". There is a gateway, a doorway between our inner life and our outer life - and we need to strive for consonance between the two. Integrity. Virtue. This is the doorway uniting the inner and the outer. Psalm 24 has a lot to teach us about this doorway:
"Who shall ascend the hill of the LORD? And who shall stand in his holy place? Those who have clean hands and pure hearts, who do not lift up their souls to what is false, and do not swear deceitfully. They will receive blessing from the LORD, and vindication from the God of their salvation. Such is the company of those who seek him, who seek the face of the God of Jacob."
Integrity, virtue, you choose your word for "those who have clean hands and pure hearts, who do not lift up their souls to what is false, and do not swear deceitfully..."
I cannot easily source this collect, but I find echoes of the collect for Thanksgiving for the Institution of Holy Baptism in the Scottish Book of Common Prayer of 1929:
O God who has united men of every nation in the confession of thy Name, and dost continually multiply thy Church with new offspring: Grant that those who have been born again of water and of the Spirit may be one both in inward faith and in outward devotion, and with thankful hearts may shew forth in their lives the grace of that Sacrament which they have received; through Jesus Christ our Lord.