More New Testament passages are invoked in these two sections to root Christian baptismal theology thoroughly in Christ’s saving efforts. What do Christians believe baptism does? GICI 5 gives a summary:
5. Baptism, the cleansing with water by the power of the living word, (Ephesians 5:26) washes away every stain of sin, original and personal, makes us sharers in God’s own life (2 Peter 1:4) and his adopted children. (Romans 8:15, Galatians 4:5) As proclaimed in the prayers for the blessing of the water, baptism is a cleansing water of rebirth (Titus 3:5) that makes us God’s children born from on high. The blessed Trinity is invoked over those who are to be baptized, so that all who are signed in this name are consecrated to the Trinity and enter into communion with the Father, the Son, and the Holy Spirit. They are prepared for this high dignity and led to it by the scriptural readings, the prayer of the community, and their own profession of belief in the Father, the Son, and the Holy Spirit.
This is a good expansion on what we read in GICI 3. While God’s grace can certainly work independently of or in spite of human ritual efforts, the liturgy of baptism is described in terms of preparing and leading the neophyte to the dignity this section cites. Three important liturgical aspects are celebrated before the actual water bath of baptism: the proclamation of the Word, the prayer of the community, and the individual’s own profession of faith. We will see ample evidence of all three in the rites of RCIA, and the expectation they will be included before the baptism of infants.
GICI 6 illustrate why the Easter Vigil and Sundays are so important:
6. Far superior to the purifications of the Old Law, baptism produces these effects by the power of the mystery of the Lord’s passion and resurrection. Those who are baptized are united to Christ in a death like his; (Romans 6:4-5) buried with him in death, they are given life again with him, and with him they rise again. (Ephesians 2:5-6) For baptism recalls and makes present the paschal mystery itself, because in baptism we pass from the death of sin into life. The celebration of baptism should therefore reflect the joy of the resurrection, especially when the celebration takes place during the Easter Vigil or on a Sunday.
For families celebrating “private” baptisms, some of the prime considerations may be convenience of guests, the timing of the day, or in a few places, superstition. I knew a priest years ago who scheduled baptisms on Saturdays (“A better day for families.”) and sometimes in consecutive liturgies on the half-hour. (“Families prefer not to share the special moment.”) It’s not to say that cookie-cutter Saturday baptisms are invalid–my own baptism of honored memory took place at 3PM on a Saturday afternoon. If believers are attuned to the importance of Sunday, the connection makes stronger the understanding that baptism is a participation in Jesus Christ. That’s a bit stronger than a cultural association with Jesus Christ.
For adults entering the faith, this is why Easter Vigil is so important. It’s not just the day, but the whole build-up of the liturgical year toward the Paschal Triduum and all it signifies for the Christian.
Can a baptized person experience Christ profoundly on any old weekday? Sure. But such an observance would lack the full weight of the Church’s liturgy and the liturgical/spiritual/devotional mindset of the faith community. In the secular sphere, Sunday may look a lot like Saturday in terms of being a day of leisure. An odd afternoon or early evening: likewise a time of leisure. But to the committed Christian, Sunday is something more. If some believers have lost the notion of Sunday, would it be more important or less important to reinforce the realm of the spiritual with Sunday celebrations?