'Solemn' in the Bible

So in my anger I swore a solemn oath that they would never enter my rest."

We who have believed are entering that rest, just as he has said, "So in my anger I swore a solemn oath that they would never enter my rest,"

For the law appoints as high priests men subject to weakness, but the word of solemn affirmation that came after the law appoints a son made perfect forever.