Catechism of the Catholic Church §527 — excerpt
Jesus' circumcision, on the eighth day after his birth, is the sign of his incorporation into Abraham's descendants, into the people of the covenant. It is the sign of his submission to the Law and his deputation to Israel's worship, in which he will participate throughout his life.
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.