'Solemn' in the Bible

Also day by day, from the first day unto the last day, he read in the book of the law of God. And they kept the feast seven days; and on the eighth day was a solemn assembly, according unto the manner.

[are] helping their brothers, their nobles, and entering into a solemn oath to walk in the law of God which was given by the hand of Moses the servant of God, and to observe and do all of the commandments of Yahweh our Lord and his judgments and regulations.