New Saint Joseph Baltimore Catechism

This catechism book says that Baptism is the door to the other sacraments, and you cannot become a Christian without being baptized. It uses John 3:5 as proof (Unless a man be born again of water and Spirit he cannot enter the Kingdom of God.). However, water here is not being used to illustrate baptism, but of repentance. It also says Baptism takes away sins, and implies that sometimes you can have no actual sin.