Some Aspects of Biblical Imagery in Piers Plowman.
WL occasionally draws his images of familiar biblical events from standard narrative and typological scenes as found in compendia in order to say several things at once. Typological exegesis of Joseph’s dream (Gen. 37:9) emphasizes the honoring of Christ and the love of God, which the Dreamer (B.7) learns is all-important in obtaining forgiveness. Moses Striking Water from a Rock (B.14.64), commonly understood as a type of the Crucifixion, offers the perfect example, in Christ’s death, of the need for our patient acceptance of God’s will. Similarly, the typological understanding of Abraham Seeing the Three Youths as a figure of the Trinity and a prefiguration of the Annunciation, and of Abraham’s Bosom as a foreshadowing of the blessed in heaven, illuminate WL’s treatment in B.16.181, 225; 17.27, 231 and 253. The Samaritan episode (B. 17), which opens with Moses Receiving the Law, is meant to recall the antitype of that scene, Pentecost.
Phillips, Langland, the Mystics and the Medieval English Religious Tradition 39-55.