Addressing the converts to Christianity in Colossae Paul wrote of their relationship with Christ by saying, “You were buried with him in Baptism.”
Those sound like rather empty holy words, but our accounts of Baptism from the early Church tell us that being “buried with him in Baptism” was something they felt about most sincerely.
In 200 a Roman priest named Hippolytus wrote a careful account of the way the Sacraments had been conferred in Rome since the time of Peter and Paul. That account, which we call the “Apostolic Tradition” described how Baptism was only conferred once a year. That was on Holy Saturday. On that night, the people commemorated Christ’s stay in the tomb on Holy Saturday. They gathered around a pool of water which for them represented Christ’s tomb.
The priest presiding reminded all present that two thieves were crucified with Jesus, with all three undergoing the same physical death. What made the death of Jesus invaluable, as St. Paul put it, wasn’t his physical death, but his death to sin.
The priest then asked those to be baptized to join in Our Lord’s death to sin by submerging themselves in the pool representing his tomb.
That is what Paul had in mind when he reminded the Christians of Colossae, “You were buried with him in Baptism.”