Seven

Numbers 29:12-38
On the fifteenth day of the seventh month, you are to hold a sacred assembly; you must not do any regular work, and you shall observe a feast for the LORD for seven days. . . .

the eighth

2 Chronicles 7:8-11
So at that time Solomon and all Israel with him--a very great assembly of people from Lebo-hamath to the Brook of Egypt--observed the feast for seven days. . . .

Nehemiah 8:18
Day after day, from the first day to the last, Ezra read from the Book of the Law of God. The Israelites kept the feast for seven days, and on the eighth day they held an assembly, according to the ordinance.

John 7:37
On the last and greatest day of the feast, Jesus stood up and called out in a loud voice, "If anyone is thirsty, let him come to Me and drink.

solemn [heb] day of restraint

Deuteronomy 16:8
For six days you must eat unleavened bread, and on the seventh day you shall hold a solemn assembly to the LORD your God, and you must not do any work.

Joel 1:14
Consecrate a fast; proclaim a solemn assembly! Gather the elders and all the residents of the land to the house of the LORD your God, and cry out to the LORD.

Joel 2:15
Blow the trumpet in Zion, consecrate a fast, proclaim a sacred assembly.