Catechism of the Catholic Church §186 — excerpt
From the beginning, the apostolic Church expressed and handed on her faith in brief formulae normative for all. But already very early on, the Church also wanted to gather the essential elements of her faith into organic and articulated summaries, intended especially for candidates for Baptism:
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.
Also cites: St. Cyril of Jerusalem, Catech. illum. 5, 12: PG 33, 521-524