11 Then, after these things, we say that Prayer which the Saviour delivered to His own disciples, with a pure conscience entitling God our Father, and saying, Our Father, which art in heaven. O most surpassing loving-kindness of God! On them who revolted from Him and were in the very extreme of misery has He bestowed such a complete forgiveness of evil deeds, and so great participation of grace, as that they should even call Him Father. Our Father, which art in heaven; and they also are a heaven who bear the image of the heavenly, in whom is God, dwelling and walking in them.
Source: Catechetical Lectures (New Advent)