Roman Catechism 16.25

Chapter 16 — Part II: The Sacraments — Baptism

Section 25. Besides the minister of the Sacrament, the person to be baptised and the principal efficient cause of Baptism should be mentioned. The pronoun thee, and the distinctive names of the Divine Persons are therefore added. Thus the complete form of the Sacrament is expressed in the words already mentioned: I baptise thee in the name of the Father, and of the Son, and of the Holy Ghost.