In Baptism and Confirmation, the handing on (traditio) of the Lord's Prayer signifies new birth into the divine life. Since Christian prayer is our speaking to God with the very word of God, those who are "born anew". . . Through the living and abiding word of God" learn to invoke their Father by the one Word he always hears. They can henceforth do so, for the seal of the Holy Spirit's anointing is indelibly placed on their hearts, ears, lips, indeed their whole filial being. This is why most of the patristic commentaries on the Our Father are addressed to catechumens and neophytes. When the Church prays the Lord's Prayer, it is always the people made up of the "new-born" who pray and obtain mercy.
Source: Catechism of the Catholic Church (Vatican.va)