'Solemn' in the Bible

For six days you shall eat unleavened bread, and on the seventh day there shall be a celebration to the Lord your God; so you shall do no work [on that day].

Seven days you shall celebrate a feast to the Lord your God in the place which the Lord chooses, because the Lord your God will bless you in all your produce and in all the work of your hands, so that you will be altogether joyful.