What do we learn from "Tzadik Ochel l'Sova Nafsho"?
Sha'arei Teshuvah 1:30: Desire arouses the Nefesh to sin, and to draw the eye to follies. A Tzadik makes a fence to guard the way of Teshuvah. He separates from pleasures, and is not drawn after desire also for permitted matters.
Orchos Tzadikim (Sha'ar ha'Ahavah DH ha'Shishi she'YInhag): A sign of humility is not engaging in pleasures.
Orchos Tzadikim (Sha'ar ha'Ahavah DH Zeh ha'Chalal): A Chacham said, I eat in order to live. A Kesil says, I live in order to eat.
Malbim #1: He does not eat to fill his stomach, only to satiate his Nefesh - what suffices, but not extras.
Malbim #2: This hints that he eats to satiate his spiritual Nefesh, based on what is needed to keep his Nefesh alive.
Erech Apayim 1 (va'Yosef Avraham 43): One who gets angry must leave a third of his stomach empty, lest it burst when he gets angry. A Tzadik (who does not get angry) can eat to fill his stomach (if he wants).
Is a Rasha's stomach always lacking?
Rashi: It does not seem to be satiated.
Malbim: Resha'im eat in order to fill their stomachs. Their stomachs always lack, for whatever a Rasha has, he desires more; there is no limit to his desire. This also answers above - R. Chanina ben Dosa, a Kav of carobs sufficed for him; he did not want more. He wanted only to satiate his Nefesh; worldly pleasures were like nothing in his eyes. The primary pleasure is spiritual, in the world to come.
