In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink." - John 7:37 KJV

What was “the last day, that great day of the feast”?

The feast that was being celebrated was the Feast of Tabernacles. This feast lasted for seven days. Jews call this feast “Sukkot,” which is Hebrew for “tabernacles.” Today, Friday October 18, is the last day of the feast. It is called “Hoshana Rabbah,” the "Great Hosanna" or "Great Salvation."

During the time of the Temple, each day water was poured on the Altar. Starting on the second night of Sukkot, there was the Water Drawing Festival.  There would be all-night celebrations in the Temple courtyard, with Levites playing instruments of music on the fifteen steps leading to the inner courtyard. Sages danced and juggled burning torches. Huge oil-burning lamps illuminated the entire city. At daybreak, a procession would make its way to the Shiloach Spring. This spring flowed in a valley below the Temple. There they would "draw water with joy."

The Talmud states that "one who has not witnessed the Festival of the Water Drawing has not seen joy in his lifetime!"

It was said the water drawing came with a great awareness of Godliness, to the degree that people would “draw” prophetic revelation.

“The Chassidic masters explain that the water celebration signifies a joy caused by a connection to God so deep and so true that, like water, it has no describable taste. And like water, it sustains all life.” (Chabad.org)

We can see that these statements describe the Holy Ghost.

It was on the last day of this feast, that Jesus “stood and cried, saying, If any man thirst, let him come unto me, and drink. He that believeth on me, as the scripture hath said, out of his belly shall flow rivers of living water. (But this spake he of the Spirit, which they that believe on him should receive: for the Holy Ghost was not yet given; because that Jesus was not yet glorified.)" - John 7:37-39 KJV

Jesus connected the outpouring of His Spirit, which would begin on the Day of Pentecost, with the great joy of the Water Drawing Festival.

Peter preached on the Day of Pentecost how to receive His Spirit – the Holy Ghost:

"Then Peter said unto them, Repent, and be baptized every one of you in the name of Jesus Christ for the remission of sins, and ye shall receive the gift of the Holy Ghost. For the promise is unto you, and to your children, and to all that are afar off, even as many as the Lord our God shall call." - Acts 2:38-39 KJV