'Solemn Assembly' in the Bible

Seven days you shall offer a fire offering to Jehovah. On the eighth day shall be a holy convocation to you. And you shall offer a fire offering to Jehovah. It is a solemn assembly. And you shall do no work of labor.

On the eighth day you shall have a solemn assembly. You shall do no laboring work.

Six days you shall eat unleavened bread. And on the seventh day shall be a solemn assembly to Jehovah your God. You shall do no work.

And in the eighth day they made a solemn assembly. For they kept the dedication of the altar seven days, and the feast seven days.