Baptism -- Bible and Catechism references
Here are some Bible references
Christians are instructed to baptize people Matthew 28:19,20 Go, therefore, and make disciples of all nations, baptizing them in the name of the Father, and of the Son, and of the holy Spirit, teaching them to observe all that I have commanded you. And behold, I am with you always, until the end of the age.
The Church began its existence with baptism Acts 2:37,38 Now when they heard this, they were cut to the heart, and they asked Peter and the other apostles, “What are we to do, my brothers?” Peter [said] to them, “Repent and be baptized, every one of you, in the name of Jesus Christ for the forgiveness of your sins; and you will receive the gift of the holy Spirit.
We contact the death and life of Christ in baptism Romans 6:4 We were indeed buried with him through baptism into death, so that, just as Christ was raised from the dead by the glory of the Father, we too might live in newness of life.
We are placed "in" Christ by baptism Galatians 3:26,27 For through faith you are all children of God in Christ Jesus. For all of you who were baptized into Christ have clothed yourselves with Christ.
Here are some references from the Catechism
Paragraph 1257 The Lord himself affirms that Baptism is necessary for salvation. He also commands his disciples to proclaim the Gospel to all nations and to baptize them. Baptism is necessary for salvation for those to whom the Gospel has been proclaimed and who have had the possibility of asking for this sacrament. The Church does not know of any means other than Baptism that assures entry into eternal beatitude; this is why she takes care not to neglect the mission she has received from the Lord to see that all who can be baptized are "reborn of water and the Spirit." God has bound salvation to the sacrament of Baptism, but he himself is not bound by his sacraments.
Paragraph 1216 (quoting Gregory Nazianzus) Baptism is God's most beautiful and magnificent gift. . . .We call it gift, grace, anointing, enlightenment, garment of immortality, bath of rebirth, seal, and most precious gift. It is called gift because it is conferred on those who bring nothing of their own; grace since it is given even to the guilty; Baptism because sin is buried in the water; anointing for it is priestly and royal as are those who are anointed; enlightenment because it radiates light; clothing since it veils our shame; bath because it washes; and seal as it is our guard and the sign of God's Lordship.