Catechism of the Catholic Church §1289 — excerpt
Very early, the better to signify the gift of the Holy Spirit, an anointing with perfumed oil (chrism) was added to the laying on of hands.
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.