“The Feast of Booths” is Tabernacles, in Hebrew Sukkot: the autumn week when Israel lived (and Jewish families still eat) in leafy shelters remembering the wilderness. In Temple times each morning of the feast a priest carried water in gold from the pool of Siloam up to the altar and poured it out, praying for the year's rain, while the crowds sang: the Mishnah calls it the Rejoicing at the Place of the Water-Drawing, and the Talmud says whoever never saw it “has never seen rejoicing in his life” (Sukkah 51a).

That is the scene on “the last day of the feast, the great day,” when Jesus stood and cried out, “If anyone thirsts, let him come to me and drink”: a claim staged inside the feast's own ceremony, at the moment all Jerusalem was thinking about water from God.