10
If the ax is dull, and one does not sharpen its edge, then one must exert more strength; however, the advantage of wisdom is that it brings success.
10
If the [hatchet's] iron [blade] is blunt, and [its user] doesn't sharpen it, he will have to exert more effort; but the expert has the advantage of his skill.
10
If iron is folded again, and it is not as before, but is made blunt, it shall be made sharp with much travail; and wisdom shall follow after busyness.