Catechism of the Catholic Church §2796 — excerpt
When the Church prays "our Father who art in heaven," she is professing that we are the People of God, already seated "with him in the heavenly places in Christ Jesus" and "hidden with Christ in God;" yet at the same time, "here indeed we groan, and long to put on our heavenly dwelling."
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: Ad Diognetum 5: PG 2, 1173