Adam Clarke on Proverbs 10:26

As vinegar to the teeth - The acid softening and dissolving the alkali of the bone, so as to impair their texture, and render them incapable of masticating; and as smoke affects the eyes, irritating their tender vessels, so as to give pain and prevent distinct vision; so the sluggard, the lounging, thriftless messenger, who never returns in time with the desired answer.