Albert Barnes Commentary Job 15:18

"(Which wise men have told From their fathers, and have not hid it;" — Job 15:18 (ASV)

Which wise men have told from their fathers - Which they have received from their ancestors and communicated to others. Knowledge among the ancients was communicated chiefly by tradition from father to son. They had few or no written records, and hence, they embodied the results of their observation in brief, pithy maxims, and transmitted them from one generation to another.

And have not hid it - They have freely communicated the result of their observations to others.