Musar sobre Provérbios 19:29

And our sages of blessed memory have already proclaimed: "one who is given to levity brings afflictions on himself" (Avodah Zara 18b). And scripture states explicitly: "Judgments are prepared for the frivolous" (Prov. 19:29). This is something reason dictates. For one who is aroused through reflection and study does not need the ordeal of bodily sufferings since he will repent of his sins even without this. He repents by means of thoughts of repentance awakening in his heart stimulated by the reading or hearing the reprimands and rebukes.

If he leaves himself in the hands of his [natural] heaviness, it is a certainty that he will not succeed. This is what the Tana (Mishnaic sage) stated: "be brazen as a leopard, light as an eagle, swift as a deer, and mighty as a lion to do the will of your Father in Heaven" (Avot 5:20). Likewise, the Sages counted among the things which need strengthening: "Torah and good deeds" (Berachot 32b). This is explicitly stated in scripture: "be strong and very courageous [to observe and do all of the Torah...]" (Yehoshua 1:6). For great strengthening is needed for one who wants to bend his nature to its opposite.

Besides the plain meaning, which is true in the literal sense, for this is indeed what happens to the field of a lazy man, the sages of blessed memory expounded it beautifully in a Midrash (Yalkut Mishlei 247:961) as follows: