See, here’s the thing. According to the Gospels, Jesus and his disciples took only three cups during the Passover meal. It was with the third one, the cup of redemption (also called the cup of blessing), that Jesus instituted the Holy Eucharist. And he said then that he wouldn’t drink again until he came into his kingdom.
On the cross, in the middle of Friday afternoon, he called out that he was thirsty, and when he’d taken a drink of the rough soldier’s mix of wine and vinegar they offered him, he said ‘It is finished’, and died.
What does it all mean? According to a theory put forward by theologian Scott Hahn, the drink on the cross was the fourth cup of the Passover. Hahn suggests that what Jesus completed by drinking it – what was finished – was the Passover meal, and also its transmogrification into the Eucharist. (The article I’ve linked to is the short version. In his full presentation, Hahn goes into a lot of detail, including the physical and medical reasons why actual thirst was unlikely.)
If this view is correct, not only does it highlight how the Eucharist and the Cross are inextricably bound together, we also need to rethink what Christ meant about coming into his kingdom.
The fourth cup of the passover, by the way, is the Cup of Restoration, based on God’s promise: “I will take you to be my people, and I will be your God.”