CCC 1228
Christian Mystery›SECTION TWO THE SEVEN SACRAMENTS OF THE CHURCH›CHAPTER ONE THE SACRAMENTS OF CHRISTIAN INITIATION›II. Baptism in the Economy of Salvation
Hence Baptism is a bath of water in which the "imperishable seed" of the Word of God produces its life-giving effect. St. Augustine says of Baptism: "The word is brought to the material element, and it becomes a sacrament."