John 7:37

ἐν δὲ τῇ ἐσχάτῃ ἡμέρᾳ … This exact specification of time is given that we may understand the significance of the words uttered by Jesus. The Feast of Tabernacles lasted for seven days (Leviticus 23:34; Nehemiah 8:18), and on the eighth day was “an holy convocation,” on which the people celebrated their entrance into the holy land, abandoning their booths, and returning to their ordinary dwellings. On each of the seven feast days water was drawn in a golden pitcher from the pool of Siloam, and carried in procession to the Temple, in commemoration of the water from the rock with which their fathers in the desert had been provided. On the eighth day, which commemorated their entrance into “a land of springs of water,” this ceremony was discontinued. But the deeper spirits must have viewed with some misgiving all this ritual, feeling still in themselves a thirst which none of these symbolic forms quenched, and wondering when the vision of Ezekiel would be realised, and a river broad and deep would issue from the Lord's house. Filled with these misgivings they suddenly hear a voice, clear and assured, Ἐάν τις διψᾷ, ἐρχέσθω πρός με καὶ πινέτω : that is, whatever natural wants and innocent cravings and spiritual aspirations men have, Christ undertakes to satisfy them every one. To this general invitation are added words so enigmatical that John finds it necessary to explain their reference.