Dear Katie:

Canon Law  846 §1 states: "In celebrating the sacraments the liturgical books approved by competent authority are to be observed faithfully; accordingly, no one is to add, omit, or alter anything in them on one’s own authority."

Any change made by the priest to any part of the Mass that is not approved by the Church is illicit. If he does this with disregard for what he knows the Church expects, then he commits a grave sin.

The change of words by this priest is certainly illicit, but the question here is the validity of the Consecration.

First, it must be said that you could have heard the words wrongly and that it only sounded like "it"; or it could have been an unintentional mistake on the priest's part. If this priest did it deliberately then we have a problem. If he continues to change the words of consecration I would certainly contact the Bishop.

Fr. Vincent Serpa, O.P, from Catholic Answers, says: "As long as the priest conveys what the Church conveys in consecrating the bread and the wine, the consecration is valid, though illicit (unlawful) if he changes the words."

This opinion is suspect, however, in my opinion. Catholics United for the Faith, in a Faith Facts article, states: "Summarizing the Church’s theological tradition, Ludwig Ott believes that “Jesus effected the transmutation by the words: ‘This is My Body,’ ‘This is My Blood’.” These words, which are never omitted in any formula of consecration, are undoubtedly essential for the validity of the sacrifice."

Ott states that the form of the consecration is Sent. certa., which means that it is definitive doctrine.

Ultimately, I would contact your bishop and ask about the validity of the consecration.

God Bless,
Bro. Ignatius Mary