Catechism of the Catholic Church

The Church thus confesses that Jesus is inseparably true God and true man. He is truly the Son of God who, without ceasing to be God and Lord, became a man and our brother: (212) > "What he was, he remained and what he was not, he assumed," sings the Roman Liturgy. And the liturgy of St. John Chrysostom proclaims and sings: "O only-begotten Son and Word of God, immortal being, you who deigned for our salvation to become incarnate of the holy Mother of God and ever-virgin Mary, you who without change became man and were crucified, O Christ our God, you who by your death have crushed death, you who are one of the Holy Trinity, glorified with the Father and the Holy Spirit, save us!"