The New Testament contains two traditions of the words that Jesus spoke when he instituted the Eucharist. The older tradition is found in St. Paul’s first letter to the Corinthians. Writing within one generation of the Last Supper itself, Paul clearly states in 1 Cor 11:23-26 that he is passing on to others what he himself has received.
On October 17, 2006, the Prefect of the Congregation for Divine Worship and the Discipline of the Sacraments sent a letter concerning the words of consecration used at the present time in the liturgy. Specifically, he said two things.
After the Sign of the Cross at the beginning of Mass, the priest may choose to greet the people with the simple and familiar greeting “The Lord be with you.” He uses this same greeting before the reading of the gospel, at the beginning of the Preface and before the final blessing.