The Lord' Supper and the Fourth Cup.         This Sunday is Palm Sunday, the beginning of Holy Week.  The Mass of the Lord’s Supper is on Holy Thursday. Th e Mass remembers when Jesus instituted the Holy Eucharist during the Jewish Passover Seder with his disciples.       The Passover Seder includes four cups of wine. The first cup has a special blessing spoken over it, followed by a serving of herbs. The Exodus Passover story is told, followed by the second cup. The main meal, consisting of lamb and unleavened bread, follows next, and afterwards the third cup, the “cup of blessing.” St. Paul seems to confirm this was the cup the Lord used in the institution of the Eucharist when he says, “The cup of blessing which we bless, is it not a participation in the blood of Christ?” ( 1 Cor 10:16 .)       Paul gives us the earliest record of what happened: “On the night when he was betrayed [Jesus] took bread, and when he had...