Musar zu Ijow 30:32

And, especially, if one has a time set aside for Torah in the house of study, how much will the trait of guarding his tongue avail his learning that it not be disturbed! For failing that he runs the risk of losing learning every day, and his learning itself will be fragmented. And the greatness of the punishment for this is well known. As Chazal have said (Avodah Zarah 3b): "If one interrupts his Torah study to engage in talk, he is fed broom-coals, as it is written (Iyyov 30:4): 'Those who interrupt maluach [(homiletically) "words written on the tablets" (luchoth)] with [idle] talk, broom-coal roots are their bread.'" And this is measure for measure. For if one studies Torah, his soul endures forever by the light of the holy Torah, which does not consume the soul (G-d forbid), but, to the contrary, sustains it eternally, as bread sustains his body in his lifetime. For this reason, Torah is called "bread," as it is written (Mishlei 9:5): "Come, eat of My bread, etc." And if he stops in the middle of his learning, he indicates that he does not want that bread, wherefore, he is fed there — instead of the food of the soul, the light of Torah — the light [i.e., the fire] of broom-coal roots.

For the cruel person feels no pain at the troubles of his companions, as you see in contrast with David who said: "As for me, when they were sick, my clothing was sackcloth, I afflicted my soul with fasting, and as for my prayer for them — may it return to my own bosom" (Ps. 35:13). And in the Book of Job it is written: "If I have not wept for him that was in trouble and if my soul grieved not for the needy" (Job 30:25). And all this is very far from the cruel man. This trait of cruelty is found only in people whose natures are like the nature of lions that prey and violently rend. When the spirit of wrath takes strong hold of a man then the quality of mercy flees, and Cruelty grows powerful to ruin and destroy as it is written: "Wrath is cruel and anger is overwhelming" (Prov. 27:4). There is no wrath like the anger of Cruelty. In the attributes of the Creator, may He be Blessed, you will find : "In wrath remember Compassion" (Hab. 3:2). But this is far from man's ability — to have mercy in the midst of his anger. And there is this aspect of the quality of Cruelty in the soul of man — to avenge himself on his enemies as it is written: "And he will not spare in the day of vengeance" (Prov. 6:14). The meaning of this verse is that where there is the desire for vengeance there is no compassion, only cruelty. And Scripture says: "You shall not avenge nor bear a grudge" (Lev 19:18). We are warned not to bear a grudge even in our heart — all the more so not to do any deed with the hands to hurt a companion. Even when your enemy has fallen through no fault of yours, you must not rejoice as it is written: "Rejoice not when your enemy falls and when he stumbles let not your heart be glad" (Prov. 24:17). The avenger or the grudge-holder never overlooks a grievance and never forgives his companions who have wronged him, and this attitude drags after it quarrels and hatred, and you already know how good and how pleasant is the quality of peace.