I received from the Lord what I also handed on to you, that the Lord Jesus, on the night he was handed over, took bread, and, after he had given thanks, broke it and said, “This is my body that is for you. Do this in remembrance of me.” In the same way also the cup, after supper, saying, “This cup is the new covenant in my blood. Do this, as often as you drink it, in remembrance of me.” For as often as you eat this bread and drink the cup, you proclaim the death of the Lord until he comes. (1 Cor 11:23-26
https://bible.usccb.org/bible/readings/040623-Supper.cfm
The oldest account of the institution of the Eucharist is this passage from Paul’s First Letter to the Corinthians. The Eucharist comes not just from the Last Supper that Jesus had with his disciples but from all the meals that Jesus shared with his disciples.