John 7:37

Now on the last day, the great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me and drink.

THE EVENTS OF THE LAST DAY OF THE FEAST

The feast of tabernacles was concluded on the final day, thus:

A high point in the ritual of Tabernacles was the pouring out in the temple court of a golden pitcher of water from the Siloam Pool. This libation was held to symbolize the future outpouring of the Holy Spirit in the Messianic age.[12]

In such a context, Jesus' cry for men to come unto him and drink was the equivalent of his promising the Holy Spirit to all who would follow him. Thus, in this Gospel, there is another recurrence of emphasis upon water. See comment under John 4:2.