Piers Plowman B.xviii. 3 7 1: ‘right ripe must.
Must in B. 18.3 71 refers to “new wine,” rather than “grape juice in the process of becoming wine.” Christ will not be able to quench his thirst until the Last judgment, when he will drink the new wine at its earliest moment when the fermenting grape has become wine. Grapes and wine in such Old Testament passages as Num. 13:24, Cant. 1: 13, Isa. 5:1-7 were interpreted in the Middle Ages as types of Christ’s Passion; Isa. 5:1-7 forms the basis of the second Tractus of Mass on Holy Saturday, and WL’s mention of the Good Friday Mass and Adoration of the Cross (B. 18) shows he had the Holy Week liturgy in mind. The comment of the Glossa ordinaria on John 19:28, Luke 23:26 and Mark 15:36 associates the vinegar of the Passion with both the Jews and the apple eaten by Adam and Eve. Through his outwitting of the Devil, Christ turns the “bitternesse” prepared for him by the “doctor of death” into the sweet wine of the Resurrection.
Stokes and Burton, Medieval Literature and Antiquities, 133-43.