Verses with the word foolishness in the Old Testament (13 verses):

2 Samuel 15:31
And one told David, saying, Ahithophel is among the conspirators with Absalom. And David said, O LORD, I pray thee, turn the counsel of Ahithophel into foolishness.

Psalms 38:5
My wounds stink and are corrupt because of my foolishness.

Psalms 69:5
O God, thou knowest my foolishness; and my sins are not hid from thee.

Proverbs 12:23
A prudent man concealeth knowledge: but the heart of fools proclaimeth foolishness.

Proverbs 14:24
The crown of the wise is their riches: but the foolishness of fools is folly.

Proverbs 15:2
The tongue of the wise useth knowledge aright: but the mouth of fools poureth out foolishness.

Proverbs 15:14
The heart of him that hath understanding seeketh knowledge: but the mouth of fools feedeth on foolishness.

Proverbs 19:3
The foolishness of man perverteth his way: and his heart fretteth against the LORD.

Proverbs 22:15
Foolishness is bound in the heart of a child; but the rod of correction shall drive it far from him.

Proverbs 24:9
The thought of foolishness is sin: and the scorner is an abomination to men.

Proverbs 27:22
Though thou shouldest bray a fool in a mortar among wheat with a pestle, yet will not his foolishness depart from him.

Ecclesiastes 7:25
I applied mine heart to know, and to search, and to seek out wisdom, and the reason of things, and to know the wickedness of folly, even of foolishness and madness:

Ecclesiastes 10:13
The beginning of the words of his mouth is foolishness: and the end of his talk is mischievous madness.