Musar zu Pirkei Avot 5:23

"nettles had covered the face of it" - since he did not labor sufficiently in the Torah, he sits in judgment and declares the pure, unclean and the impure, clean, thus breaching the fence set up by the Torah Sages. What is his punishment? Shlomo revealed it: "one who breaches a fence will be bitten by a snake" (Kohelet 10:8).

A person could have sat idle and the decree would have been fulfilled (his designated portion would have come to him), had it not been preceded by the fine imposed on every human being: "by the sweat of your brow shall you eat bread" (Gen.3:19), whereby a person is required to make some effort for obtaining his livelihood, for thus the exalted King decreed.