Albert Barnes Commentary 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." — John 7:37 (ASV)

In the last day. This refers to the eighth day of the festival.

That great day. This was the day of the holy convocation or solemn assembly (Leviticus 23:36). This day seems to have been called the great day for several reasons:

1. Because of the solemn assembly and because it was the closing scene.
2. Because, according to their traditions, on the previous days they offered sacrifices for the Gentile nations as well as for themselves, but on this day for the Jews only (Lightfoot).
3. Because on this day they abstained from all servile labor (Leviticus 23:39) and regarded it as a holy day.
4. Because on this day they finished the reading of the Law, which they began at the start of the feast.
5. Because on this day the ceremony of drawing water from the pool of Siloam probably occurred.

On the last day of the feast, it was customary to perform a solemn ceremony in this manner: the priest filled a golden vial with water from the spring of Siloam (see the notes on John 9:7). This water was carried with great solemnity, accompanied by the clangor of trumpets, through the gate of the temple. After being mixed with wine, it was poured on the sacrifice on the altar.

The origin of this custom is unknown. Some suppose, and not improbably, that it arose from a misunderstanding of the passage in Isaiah 12:3: With joy you shall draw water out of the wells of salvation. It is certain that no such ceremony was commanded by Moses.

It is supposed to be probable that Jesus stood and cried out while they were performing this ceremony, so that he might:

1. Illustrate the nature of his doctrine by this; and
2. Call their attention away from a rite that was not commanded and that could not confer eternal life.

Jesus stood. He stood in the temple, in the midst of thousands of people.

If any man thirst. This refers to spiritual thirst. It means if anyone feels their need for salvation (Matthew 5:6; Revelation 22:17).

The invitation is full and free to all.

Let him come to me and drink. Instead of depending on this ceremony of drawing water, let him come to me, the Messiah, and he will find an ever-abundant supply for all the needs of his soul.