Musar su Proverbi 23:17

He whose nature is overcome by this disposition is blameworthy, for it leads him to envy, and a noble man is never found to be envious. Books (i.e., of poetry) have been filled with the censure of envy, and every man of intelligence knows how much has been said as to its baseness. It is necessary to turn from it, for frequently the affairs of the envious lead him to use violence. Thus it is said of such as these (Micah ii. 2), "And they covet fields and take them by violence." Enviousness is a loathsome trait. The wise man must keep himself as far from it as he can, for he gains no advantage through it: on the contrary, continued depression and fatigue of the spirit through desires and the constant hatred of men, scantiness of repose, preoccupation of the mind, apprehensiveness and the punishment of God, for transgressing that which He forbade in His revealed Scripture. Man must not be jealous of unrighteous men, because he sees them devote themselves to pleasure and (the gratifying of) passions. But let him employ his zeal in the service of God. Thus the sage said (Prov. xxiii. 17), "Let not thy heart be envious of the sinners." Again he spake (Ps. xxxvii. i), "Be thou not envious against the workers of iniquity."

Concerning solitude, the main thing is to remain at home. Even your visit to the synagogue should be very short. In fact, it is better to pray at home, for it is impossible to be spared from jealousy or from hearing idle talk or lashon hara in the synagogue. And one receives punishment for this, as we find (Shabbos 33a), "Also one who hears and is silent...." This is even the more so on Shabbos and Yom Tov when they gather to talk - It is then better that you don't pray at all. Refrain also from going to the cemetery (especially women), as it leads to all kinds of sorrow and sin. It is also advisable that your daughter not go to the synagogue, because she'll see beautiful clothes there, become jealous and talk about it at home. This will lead to lashon hara, etc. She should rather cling to Mussar and not become jealous of anything in this world, where everything is vanity and illusions, appearing and disappearing overnight (Yonah 4:10). "Though he grows as high as the sky, his head reaching the clouds, he perishes forever..." (Iyov 20:6,7). "For property does not last forever, or a crown for all generations" (Mishlei 27:24). And even while it exists it is worthless, loathsome and disdained by any sensible person. Woe to him who is impressed by it. Envy only the fear of Hashem (ib. 23:17). She should not say, "How can I earn a share in the World-to-Come? - I can't do it!" For we have learned (Berachos 17a): "One may do much or one may do little, provided he directs his heart to heaven."

There is another way to intelligently understand how jealousy and lust are very ruinous qualities, and in this vein Solomon said : "Let not thy heart envy sinners, but be in the fear of the Lord all the day" (Prov. 23:17). When a man envies sinners seeing their wealth and prosperity and sees righteous men growing poorer and being sore afflicted, and, from all of this, his soul rejects reverence for God and His judgements, and rejects those who study the Torah and fulfill it, as it is said : "Your words have been all too strong against Me, saith the Lord. Ye have said : 'It is vain to serve God; and what profit is it that we have kept His charge, and that we have walked mournfully because of the Lord of Hosts? And how we call the proud happy, yea, they that work wickedness art built up; yea, they try God and are delivered" (Malachi 3:13-15).

Even though jealousy is a very bad quality, there are instances where it can be a very good quality and, in fact, it can be a most noble quality, — when one envies those who revere God, as it is said : "Let not thy heart envy sinners, but those that fear the Lord all the day…" (Prov. 23:17). And in the same way our Sages said : "that the jealousy of wise men increases wisdom" (Baba Bathra 21a). When one sees another studying, it should excite his envy and he should say "This man studies all day, I shall do the same!" And similarly in the matter of all he commandments. Everyone should envy his companion and try to emulate the good deeds of his companion. If he sees a wicked man who has even one good quality, he should envy him for that and should emulate it. But a man who envies his companion when he sees him occupying himself with Torah and with good deeds and does not envy him in order to emulate him, and does not say to himself, "This man is doing thus; I will also do thus!" but rather thinks in his heart enviously, "Because this companion has more good qualities than I, because of all this he is more honored by men," and then this envious man will plot how to confuse and take his companion away from the study the Torah and good deeds, such envy is a grievous disease, and he who deals in such envy is a sinner and one who causes others to sin. He is truly a partner of Jereboam, the son of Nebat.