Six days

Exodus 12:15, 16
For seven days you must eat unleavened bread. On the first day you are to remove the yeast from your houses. Whoever eats anything leavened from the first day through the seventh must be cut off from Israel. . . .

Exodus 13:7, 8
Unleavened bread shall be eaten during those seven days. Nothing leavened may be found among you, nor shall yeast be found anywhere within your borders. . . .

Leviticus 23:6-8
On the fifteenth day of the same month begins the Feast of Unleavened Bread to the LORD. For seven days you must eat unleavened bread. . . .

Numbers 28:17-19
On the fifteenth day of this month, there shall be a feast; for seven days unleavened bread is to be eaten. . . .

solemn assembly [heb] restraint

Leviticus 23:36
For seven days you are to present an offering made by fire to the LORD. On the eighth day you are to hold a sacred assembly and present an offering made by fire to the LORD. It is a solemn assembly; you are not to do any regular work.

2 Chronicles 7:9
On the eighth day they held a solemn assembly, for the dedication of the altar had lasted seven days, and the feast seven days more.

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.

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.