Baptism of a child in the Ancient Church
from the catacombs of St Callistus in Rome
When Jesus rose from the dead, He brought humanity to a new kind of life, higher than even that enjoyed by Adam and Eve before they fell in sin. This new kind of life is shown in the Lord’s glorified body after the resurrection : agile, bright, able to walk through barriers, incapable of suffering, and yet a human body which talks, walks and even eats (barbequed fish!).
These are the physical manifestations of a human soul perfectly united with God. Through His grace, we can become that. We can share in His divine glory, just as He shared in our broken humanity.
So how is this done? The beginning is baptism. Baptism is the application of Christ’s hard-won salvation, paid for by His blood, on the individual soul. “No one can enter the Kingdom of God without being born of water and the Spirit.” (John 3:5) “Whoever believes and is baptized will be saved.” (Mark 16:16) And the Lord commanded His Apostles to go out and teach and baptize the whole world (Matthew 28:19-20).
Since baptism and all the sacraments, for that matter, flow from the saving acts of Christ suffering, dying and rising again, Easter is the time par excellence for celebrating this sacrament. In the early Church, adult converts (catechumens) were baptized at the Easter Vigil and given white garments (albs, from the Latin word for “white,” albus), which they wore all week long! They came to Mass every day during the Octave, to be further grounded in the faith they just entered.
That is why the Masses during the Octave have a lot of references to baptism. It is the Church’s way of reinforcing the faith of the newly-baptized, and ours as well.
Collect from Easter Tuesday
The prayer speaks of "new offspring" of the Church. The Church has children who are born spiritually into the family of God. These are the ones baptized at Easter. They became the adopted children of God through the "sacrament which they have received by faith."
Collect from Easter Thursday
The prayer speaks of those "born again of water in baptism." But it already points us to Pentecost, which reverses the curse of Babel when humanity was further divided through the multiplication of languages so that men couldn't understand each other. The faith unites us, who are different in race and language.