Catechism of the Catholic Church §920 — excerpt
Without always professing the three evangelical counsels publicly, hermits "devote their life to the praise of God and salvation of the world through a stricter separation from the world, the silence of solitude and assiduous prayer and penance."
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: CIC, can. 603 # 1