2 During the Great Jubilee of the Year 2000 I had an opportunity to celebrate the Eucharist in the Cenacle of Jerusalem where, according to tradition, it was first celebrated by Jesus himself. The Upper Room was where this most holy Sacrament was instituted . It is there that Christ took bread, broke it and gave it to his disciples, saying: “Take this, all of you, and eat it: this is my body which will be given up for you” (cf. Mt 26:26; Lk 22:19; 1 Cor 11:24). Then he took the cup of wine and said to them: “Take this, all of you and drink from it: this is the cup of my blood, the blood of the new and everlasting covenant. It will be shed for you and for all, so that sins may be forgiven” (cf. Mk 14:24; Lk 22:20; 1 Cor 11:25). I am grateful to the Lord Jesus for allowing me to repeat in that same place, in obedience to his command: “Do this in memory of me” ( Lk 22:19), the words which he spoke two thousand years ago. Did the Apostles who took part in the Last Supper understand the meaning of the words spoken by Christ? Perhaps not. Those words would only be fully clear at the end of the Triduum sacrum , the time from Thursday evening to Sunday morning. Those days embrace the myste- rium paschale ; they also embrace the mysterium eucharisticum .
Source: Ecclesia de Eucharistia (Vatican.va)