Ecclesiastes 10:10

“If the iron be blunt, and he do not whet the edge, then must he put to more strength: but wisdom is profitable to direct...”

Jeremiah 31:29

“In those days they shall say no more, The fathers have eaten a sour grape, and the children’s teeth are set on edge.”

Jeremiah 31:30

“But every one shall die for his own iniquity: every man that eateth the sour grape, his teeth shall be set on edge.”

Ezekiel 18:2

“What mean ye, that ye use this proverb concerning the land of Israel, saying, The fathers have eaten sour grapes, and th...”