CCC 2777 In the Roman liturgy, the Eucharistic assembly is invited to pray to our heavenly Father with filial boldness; the Eastern liturgies develop and use similar expressions: “dare in all confidence,” “make us worthy of. .. ” From the burning bush Moses heard a voice saying to him, “Do not come near; put off your shoes from your feet, for the place on which you are standing is holy ground.”¹ Only Jesus could cross that threshold of the divine holiness, for “when he had made purification for sins,” he brought us into the Father’s presence: “Here am I, and the children God has given me.”²
Our awareness of our status as slaves would make us sink into the ground and our earthly condition would dissolve into dust, if the authority of our Father himself and the Spirit of his Son had not impelled us to this cry. .. ‘Abba, Father!’. .. When would a mortal dare call God ‘Father,’ if man’s innermost being were not animated by power from on high?³

1 Ex 3:5.
2 Heb 1:3; 2:13.
3 St. Peter Chrysologus, Sermo 71, 3: PL 52, 401 CD; cf. Gal 4:6.