With humble spirit and contrite heart Ps 51:17; Isa 66:2This prayer has been completely reworded to match the Latin more closely and to better reflect the content of the prayer and the Scripture behind it. The prayer evokes the words of King David and of Azariah, one of the three Israelites thrown into a fiery furnace by Nebuchadnezzar.
may we be accepted by you, O Lord, Dan 3:39
and may our sacrifice in your sight this day Rom 12:1; Eph 5:2
be pleasing to you, Lord God. Phil 4:18; Col 1:10
Psalm 51 was written by David after Nathan the prophet confronted him about his sin with Bathsheba, the wife of Uriah. David had seen and coveted her, committed adultery, and covered up the result by having Uriah killed in battle. (2 Sam 11) David had broken three of the Ten Commandments! (Ex 20:13,14,17) The psalm reflects his true contrition and God’s rich mercy, but also the recognition that God does not accept an insincere sacrifice, a purely external one: “Outward sacrifice, to be genuine, must be the expression of spiritual sacrifice.” (Catechism 2100)
Several centuries later, after Israel had split in two and its people had gone into exile, three Israelite youths – Azariah, Mishael, and Hananiah – were being put to death by Nebuchadnezzar for refusing to bow down and worship the golden idol he had made. (Dan 3) He threw them into a blazing furnace, but God kept them safe from harm. In the midst of the flames, Azariah offered a prayer of thanks and contrition to God. In his prayer, he asked that he and his companions would be received in God's sight as a living sacrifice, offered “with a contrite heart and a humble spirit.”
Along with the bread and wine (and eventually the Eucharist), we are offering ourselves to God. This is expressed very clearly, for example, in Eucharistic Prayer III: “May [Jesus] make of us an eternal offering to you.” This is what the Council Fathers at Vatican II had in mind when they wrote of the laity that
all their works, prayers and apostolic endeavors, their ordinary married and family life, their daily occupations, their physical and mental relaxation, if carried out in the Spirit, and even the hardships of life, if patiently borne – all these become “spiritual sacrifices acceptable to God through Jesus Christ.” Together with the offering of the Lord’s body, they are most fittingly offered in the celebration of the Eucharist. (Lumen Gentium 34)