During the Preparation of the Altar and the Gifts, various movements are made. The gifts of bread and wine are processed forward by members of the liturgical assembly and received by the presider at the altar (GIRM 73). The priest pours water into the wine. Finally, after incensing, usually the server pours a good quantity of water on both the fingers and the hands of the presider, who then uses a towel to dry his fingers and hands fully. The priest says inaudibly while washing his hands, “Lord, wash away my iniquity; cleanse me from my sin” (Roman Missal 28, p.530 ). Because the prayer is inaudible, and because in most parishes music is being sung during the preparation rites, members of the liturgical assembly do not hear the personal prayer of the priest while washing his hands, yet see the washing of his hands. Thus, the question is often asked, “Why does the priest wash his hands at Mass?”.
The General Instruction of the Roman Missal states that “The priest then washes his hands at the side of the altar, a rite that is an expression of his desire for interior purification” (GIRM 76). Thus, more than cleansing the hands is suggested by this prayer. Many of us tend to believe that the washing of his hands is a physical cleansing of the hands. Rather, the priest’s prayer during the washing is about the interior dimension of the priest so that he may be purified. The prayer also confirms this desire so that he may be cleansed from his sin and freed from iniquity. In the prayer, twice “my” is used to express that this is for the priest’s personal benefit.
Let us accompany the priest asking for forgiveness for our sins and faults so that we can be ready to receive the bread and wine now transformed into the body and blood of our Lord Jesus Christ.
Seaman, Kristopher “Why Does the Priest Wash His Hands during Mass? Liturgy Training Publications https://pastoralliturgy.org/resources/1009ReproRsrc.pdf