Passover, manna, sacrificial blood, and wisdom-banquet traditions contribute to the imagery without reducing it to a single background.
Exodus 12; Exodus 16; Proverbs 9:1-6 are useful backgrounds.
The theological point for this database is not a particular sacramental interpretation but Jesus' claim that eternal life depends upon receiving him.
Jesus places himself personally at the center of eternal life and future resurrection.
Many disciples find the teaching hard and later withdraw.