Musar su Proverbi 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:

And a man may flatter his wife for the sake of peace in his home, and he may flatter his creditor so that he does not oppress him, and his teacher so that he will teach him Torah. And it is a very good deed to flatter one's pupils or companions so that that they will study and hearken to his words, accepting his reproof to observe the commandments. Likewise one may flatter any man where he thinks that he will thereby draw him to him, so that he will listen to him, and perform the commandments. If he were to come to him with anger, the man would not listen to him, but if he comes to him with flattery, the man will accept his rebuke. In such a case, it is a very good deed to flatter him in order to bring forth the precious from the vile. For there is a man that will not accept a rebuke when it is delivered with scolding, but will when it is done gently, as it is said, "The words of the wise spoken in quiet" (Eccl. 9. 17). There are times, however, when scolding is necessary, as it is said, "A rebuke entereth deeper into a man of understanding" (Prov. 17:10). And there are times when even a lashing is proper, as it is said, "And stripes for the back of fools" (Prov. 19:29). And there are times when even a lashing will do no good, as it is said, "Than a hundred stripes unto a fool" (Prov. 17:10). If so, what shall we do to him? There is no way of correcting him, therefore you must drive him away.