Christ instituted the Eucharist

Read the Catechism in a Year

Catechism in a Year: Day 179

Part Two: How We Celebrate the Christian Mysteries
- Section Two: The Seven Sacraments of the Church
-- Chapter One: The Sacraments of Initiation -- THE EUCHARIST

Question 209: When did Christ institute the Eucharist?

Christ instituted the Holy Eucharist on the evening before his death, “on the night when he was betrayed” (1 Cor 11:23), when he gathered the apostles around him in the Upper Room in Jerusalem and celebrated the Last Supper with them.

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Question 210: How did Christ institute the Eucharist?

“For I received from the Lord what I also delivered to you, that the Lord Jesus on the night when he was betrayed took bread, and when he had given thanks, he broke it, and said, ‘This is my body, which is for you. Do this in remembrance of me.’ In the same way also the chalice, after supper, saying, ‘This chalice is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me’” (1 Cor 11:23–25).

This, the oldest account of the events in the Upper Room at the Last Supper, is by the apostle Paul, who was not an eyewitness himself, but rather wrote down what was being preserved as a holy mystery by the young Christian community and was being celebrated in the liturgy. 

Dig Deeper: Corresponding CCC section (1337-1344) and other references here.
(NOTE: We will cover the CCC sections we skipped over the next couple days).

Recommended Reading: 7 Secrets of the Eucharist by Vinny Flynn