17th Sunday in Ordinary Time, Luke 11:1-13
Though it might at first seem odd, we must admit that the “Our Father” prayer refers to the whole Trinity, Father, Son, and Holy Spirit – the Father is “Our Father,” the Son is “Our Father,” and the Holy Spirit is “Our Father.” That being said, “Our Father” refers in a special way to God the Father; not, however, so as to exclude the Son or the Holy Spirit.
First, if you remember your catechism, you will recall that “everything [in the Trinity] is one where there is no opposition of relationship” (Council of Florence, cited in the Catechism of the Catholic Church 255). This means that everything that the Father is, so also is the Son, excepting that he is not the Father. So, as the Father is God, so too the Son is God. As the Father is the Creator, so too the Son is the Creator. Moreover, as the Father is worshiped, so too the Son is worshiped. This means that whenever we pray to the Father, we also pray to the Son and to the Holy Spirit. For the three are equal in all things, excepting that one is the Father of the Son, one is the Son of the Father, and one is the Spirit of the Father and the Son.
What does this mean for us? It means that whatever we say of God the Father, we also must say of God the Son and of God the Holy Spirit (excepting their Trinitarian relations). So, if we pray to God the Father, calling him “Our Father;” we also invoke the Son, calling him “Our Father.” For “Our Father” is first and foremost the Blessed Trinity, who created us and redeemed us.
Still, it is also equally certain that, by a certain fittingness we invoke God the Father in a particular way when we pray, “Our Father.” For, although “the personal relation of the Son to the Father is something man cannot conceive of nor the angelic powers even dimly see … the Spirit of the Son grants a participation in that very relation to us who believe that Jesus is the Christ and that we are born of God” (CCC 2780).
The whole Trinity is “Our Father” and, through the redemption won for us in Christ Jesus, we participate in his Divine Filiation as sons in the Son.
See also, ST I, q.33, a.3 - “Whether this name ‘Father’ is applied to God, firstly as a personal name?”