Musar do Przysłów 17:11

But the one who does not get aroused by the voice of his rebukers will double his iniquities. For they reprimanded him and he hardened his heart - as it is stated (Proverbs 17:10-11), "A rebuke works on an intelligent man, more than one hundred blows on a fool. An evil man seeks only to rebel; a cruel messenger will be sent against him." The explanation is that the evil man will not submit to the voice of the rebukers. Rather he will seek to rebel. And since he did not stop from the words of the reprimanding angel, a cruel angel will be sent against him - measure for measure. For rebukers are called angels (malakhim, which literally means messengers), as it is stated (II Chronicles 36:16), "But they mocked the messengers of God and disdained His words and taunted His prophets." And King Solomon, peace be upon him, also said (Proverbs 15:10), "Discipline seems bad to him who forsakes the way; he who spurns rebuke will die." Its explanation is [that] it is true that harsh rebuke is appropriate for one who has forsaken the way and transgresses the words of the Torah. However there is hope that he will take the rebuke and repent from his evil way. But worse than him is one who hates rebuke. For he has no hope and rectification from harsh rebuke. Rather his one verdict is to die. For one who does a transgression - his desire overpowered him and the impulse pushed him. But it is likely that his soul is bitter about that which he was [not stronger] in the face of his impulse. And maybe he longs for reprimand and hopes for reproof. But one who hates reprimand has already abandoned his soul; and his hatred for reprimand will be a proof that he hates the words of God, may He be blessed.

Cruelty is the opposite of Mercy as it is written: "They are cruel and have no compassion" (Jer. 50:42). And this trait of cruelty is not found in righteous people but in the souls of the wicked as it is written: "The tender mercies of the wicked are cruel" (Prov. 12:10). This quality is also found in the impudent as it is written: "An impudent nation that shall have no regard for the person of the old and show no mercy to the young" (Deut. 28:50). And you already know the evil of the trait of impudence. Go forth and learn the evil nature and the punishment of cruelty, for in the matter of the reward of a wicked man — rebellious and disobedient — it is said: "A rebellious man seeks only evil, therefore, a cruel messenger shall be sent against him" (Prov. 12:11). Every cruel person has no quality of kindness in his make up, even towards himself, as it is written: "The merciful man does kindness to his own soul, but he that is cruel troubles his own flesh" (Ibid. 11:17).