Catechism of the Catholic Church §1321 — excerpt
When Confirmation is celebrated separately from Baptism, its connection with Baptism is expressed, among other ways, by the renewal of baptismal promises. the celebration of Confirmation during the Eucharist helps underline the unity of the sacraments of Christian initiation.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.