Catechism of the Catholic Church §2788 — excerpt
Since the Lord's Prayer is that of his people in the "endtime," this "our" also expresses the certitude of our hope in God's ultimate promise: in the new Jerusalem he will say to the victor, "I will be his God and he shall be my son."
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.