Episode 681: The Catechism of the Council of Trent - Lesson 2 - "Sacraments" 1. Baptism

Baptism is the sacrament by which a person, whether a baby, child, or adult, receives an indelible spiritual mark, is cleansed of all sin and is reborn into the family of God, being sanctified by Christ to everlasting life by means of the sign of water and the action of the Holy Spirit.

The Catechism of the Council of Trent gives this definition:

“The Sacrament of regeneration by water in the word. By nature we are born from Adam children of wrath, but by Baptism we are regenerated in Christ, children of mercy. For He gave power to men to be made the sons of God, to them that believe in his name, who are born, not of blood, nor of the will of the flesh, nor of the will of man, but of God.”