Features Added Later. A custom that came to be practiced later, possibly alluded to in the Christian Greek Scriptures (Joh 7:37, 38) but not in the Hebrew Scriptures, was the drawing of water from the Pool of Siloam and pouring it, along with wine, on the altar at the time of the morning sacrifice. According to most scholars, this occurred on seven days of the festival but not on the eighth. The priest would go to the Pool of Siloam with a golden pitcher (except on the opening day of the festival, a sabbath, when the water was taken from a golden vessel in the temple, to which it had been carried from Siloam on the preceding day). He would time himself so as to return from Siloam with the water just as the priests in the temple were ready to lay the pieces of the sacrifice on the altar. As he entered the Court of the Priests by the temple Water Gate he was announced by a threefold blast from the priests’ trumpets. The water was then poured out into a basin leading to the base of the altar, at the same time that wine was being poured into a basin. Then the temple music accompanied the singing of the Hallel (Psalms 113-118), during which time the worshipers waved their palm branches toward the altar. This ceremony may have reminded the joyful celebrators of Isaiah’s prophetic words: “With exultation you people will be certain to draw water out of the springs of salvation.”​—Isa 12:3.

Jesus probably alluded to the spiritual significance of the Festival of Booths and perhaps to the ceremony with the water of Siloam when “on the last day, the great day of the festival, Jesus was standing up and he cried out, saying: ‘If anyone is thirsty, let him come to me and drink. He that puts faith in me, just as the Scripture has said, “Out from his inmost part streams of living water will flow.”’” (Joh 7:37, 38)