OT Hell

What if there is no mention of eternal punishment in the whole of the Old Testament?  What if the word Hades (the only word sometimes translated hell in the OT) was never meant to convey the meaning of eternal punishment?  Wouldn't God, when He talked to Moses on the mountain, have told him of such a place, if such a place existed? (Something like:  Oh, by the way, if you don't keep my commandments you'll end up in a place of eternal punishment.  And the people you'll be killing on the way to the promised land, they'll end up there, too.)