Council of Trent: Session V, Original Sin, Declaration 4

DECREE CONCERNING ORIGINAL SIN

4. If any one denies, that infants, newly born from their mothers' wombs, even though they be sprung from baptized parents, are to be baptized; or says that they are baptized indeed for the remission of sins, but that they derive nothing of original sin from Adam, which has need of being expiated by the laver of regeneration for the obtaining life everlasting,--whence it follows as a consequence, that in them the form of baptism, for the remission of sins, is understood to be not true, but false, --let him be anathema. For that which the apostle has said, By one man sin entered into the world, and by sin death, and so death passed upon all men in whom all have sinned, is not to be understood otherwise than as the Catholic Church spread everywhere hath always understood it. For, by reason of this rule of faith, from a tradition of the apostles, even infants, who could not as yet commit any sin of themselves, are for this cause truly baptized for the remission of sins, that in them that may be cleansed away by regeneration, which they have contracted by generation. For, unless a man be born again of water and the Holy Ghost, he cannot enter into the kingdom of God.

Translation: J. Waterworth, The Canons and Decrees of the Council of Trent (1848), Hanover Historical Texts Project transcription (1995).