During or after the recitation of the Lamb of God litany, the priest bows with hands folded and says quietly one of a couple of private prayers for personal humility and hope. Literally, the priest prays for mercy and to be worthy of his vocation in offering the Mass. The prayers are offshoots from the long defunct Gallican liturgy. The longer one goes back to the Sacramentary of Amiens in the ninth century. The shorter prayer is known in the tenth century.
An old pastor I knew would purposely tweak the prayers and say them louder than directed by the rubrics with the expectation that congregants might make them their own. While I would not make this deviation, congregants could certainly follow along in their missals. The priest’s reception of Holy Communion is preceded by one of two prayers before the Ecce Agnus Dei exhortation:
“Lord Jesus Christ, Son of the living God, who, by the will of the Father and the work of the Holy Spirit, through your Death gave life to the world, free me by this, your most holy Body and Blood, from all my sins and from every evil; keep me always faithful to your commandments, and never let me be parted from you.”
“May the receiving of your Body and Blood, Lord Jesus Christ, not bring me to judgment and condemnation, but through your loving mercy be for me protection in mind and body and a healing remedy.”
The first and longer prayer, signifies a fairly complete theology of what we are about. It begins with an address to the Lord within the context of the Trinity. Along with this it speaks of the Trinity as active or dynamic: “living God,” “will of the Father,” “work of the Holy Spirit,” and “gave life.” It concludes with a personal petition of the celebrant: “free me” from all sin and evil, “keep me faithful,” and “never let me be parted.”
The second prayer is similar to the first, and the priest according to the current rubrics may say either. Many still say both. While somewhat redundant, the latter prayer focuses upon protection from unworthy reception (1 Cor. 11 :29). Note that the constant point about worthiness and the danger of conviction by the sacrament begins not with politicians, celebrities or the laity in general— but with the priest, himself. What we repeatedly hear in the public forum is the echoing of his personal concern. No priest wants to be counted among the hypocritical scribes and Pharisees, or worse yet, with Judas.
The priest prays for unity with Christ. The Church teaches that the sacraments are effective, even if the priest is unworthy and in sin. However, in practice, the scandal of poor witness can do incalculable harm to the body of the Church. A faithful priest begs that he may so reflect the Lord that the people will welcome the presence of Jesus Christ both in the minister and in the sacrament.