The Catechism in Questions & Answers

163. How did Jesus institute Holy Communion?

Jesus was together with the twelve Apostles and celebrated the feast of Passover with them. Judas Iscariot, who had previously visited Jesus’ enemies in order to betray Him, was thus also present. As they sat together at the table, the Lord instituted Holy Communion:
“And as they were eating, Jesus took bread, blessed and broke it, and gave it to the disciples and said, ‘Take, eat; this is My body.’ Then He took the cup, and gave thanks, and gave it to them, saying, ‘Drink from it, all of you. For this is My blood of the new covenant, which is shed for many for the remission of sins” (Matthew 26: 26-28).
During this meal Jesus identified His betrayer, Judas Iscariot. After this the latter left their fellowship. He went away “and it was night” (John 13: 30).

Holy Communion: see Questions 494. et seq.