What are the
LAVABO BOWL and PITCHER?
is Latin for "I will wash." The lavabo bowl and pitcher are two items used to wash the fingers of the main celebrant of the Mass before he consecrates the bread and wine. The bowl catches the water poured out by the pitcher.
washing of the hands
occurs in all rites of the Catholic Church, but is employed at different times. In the Roman Rite, it happens at the end of the Offertory.
The washing of the priest's hands before he touches the consecrated Host reflects the need to be spiritually purified before the Lord as reflected in the priest's prayer as the water is being poured: "Wash me, oh Lord, from my iniquity, and cleanse me from my sin."
Expert taken from
The Sacred that Surrounds Us
, by Andrea Zachman, pg. 62