The Church began on the Cross. As Eve came from the sleeping side of Adam, so the Church came from the side of Christ sleeping, the sleep of death on the Cross. When St. Longinus thrust the lance through the side of Christ, blood and water flowed forth, (John 19:31-37) the water to signify Baptism, (John 3:5) and the blood to signify His Blood given to us in the New Covenant.
Both elements are necessary to be a member of the Church. The Sacraments of Christian Initiation are the same today as they were when St. Paul entered the Church after his encounter with Christ on the road to Damascus. (Acts 9:1-9) Throughout the Gospels, after someone encountered Christ, He would tell them to go show themselves to the Priest. (Luke 17:11-14) (Luke 5:12-14) St. Paul was no different. (Acts 9:10-19) Ananias, who was a bishop, gave Paul the three Sacraments of Christian Initiation: Baptism, the cleansing of sin by the water, the Spirit through the laying on of hands, and he was fed the Eucharist, the Body and Blood of Christ.
The effects are powerful as you can read in Sacred Scriptures. (Acts 9:20-22) The Father calls all people to Christ, (John 6:44-45) and through the waters of Baptism and His Body and Blood, Christ receives them. So that when we present ourselves in Heaven, we will have taken on Christ’s likeness, and the Father will welcome us home. (Matthew 25:21) Well, good and faithful servant, come into your Father’s house!