פסחים סו:ב
ריש לקיש אמר
כל אדם שכועס אם חכם הוא חכמתו מסתלקת ממנו אם נביא הוא נבואתו מסתלקת ממנו
אם חכם הוא חכמתו מסתלקת ממנו ממשה דכתיב ויקצוף משה על פקודי החיל וגו׳ וכתיב ויאמר אלעזר הכהן אל אנשי הצבא הבאים למלחמה זאת חקת התורה אשר צוה ה׳ את משה וגו׳ מכלל דמשה איעלם מיניה
Psachim 66:b
Similarly, Reish Lakish said: Any person who becomes angry, if he is aTorah scholar, his wisdom departs from him, and if he is a prophet, his prophecy departs from him. The Gemara explains: That if he is a Torah scholar his wisdom departs from him is learned from Moses, as it is written: “And Moses became angry with the officers of the host, the captains over thousands and the captains over hundreds, who came from the battle” (Numbers 31:14). And what was his punishment? As it is written afterward: “And Elazar the priest said to the men of war who went to the battle: This is the statute of the law, which the Lord commanded Moses” (Numbers 31:21), which proves by inference that this law had become hidden from Moses due to his anger.
(ג) וְיֵשׁ דֵּעוֹת שֶׁאָסוּר לוֹ לָאָדָם לִנְהֹג בָּהֶן בְּבֵינוֹנִית אֶלָּא יִתְרַחֵק מִן הַקָּצֶה הָאֶחָד עַד הַקָּצֶה הָאַחֵר....
וְכֵן הַכַּעַס מִדָּה רָעָה הִיא עַד לִמְאֹד וְרָאוּי לָאָדָם שֶׁיִּתְרַחֵק מִמֶּנָּה עַד הַקָּצֶה הָאַחֵר. וִילַמֵּד עַצְמוֹ שֶׁלֹּא יִכְעֹס וַאֲפִלּוּ עַל דָּבָר שֶׁרָאוּי לִכְעֹס עָלָיו. וְאִם רָצָה לְהַטִּיל אֵימָה עַל בָּנָיו וּבְנֵי בֵּיתוֹ אוֹ עַל הַצִּבּוּר אִם הָיָה פַּרְנָס וְרָצָה לִכְעֹס עֲלֵיהֶן כְּדֵי שֶׁיַּחְזְרוּ לַמּוּטָב יַרְאֶה עַצְמוֹ בִּפְנֵיהֶם שֶׁהוּא כּוֹעֵס כְּדֵי לְיַסְּרָם וְתִהְיֶה דַּעְתּוֹ מְיֻשֶּׁבֶת בֵּינוֹ לְבֵין עַצְמוֹ כְּאָדָם שֶׁהוּא מְדַמֶּה כּוֹעֵס בִּשְׁעַת כַּעֲסוֹ וְהוּא אֵינוֹ כּוֹעֵס. אָמְרוּ חֲכָמִים הָרִאשׁוֹנִים כָּל הַכּוֹעֵס כְּאִלּוּ עוֹבֵד עֲבוֹדַת כּוֹכָבִים. וְאָמְרוּ שֶׁכָּל הַכּוֹעֵס אִם חָכָם הוּא חָכְמָתוֹ מִסְתַּלֶּקֶת מִמֶּנּוּ וְאִם נָבִיא הוּא נְבוּאָתוֹ מִסְתַּלֶּקֶת מִמֶּנּוּ. וּבַעֲלֵי כַּעַס אֵין חַיֵּיהֶם חַיִּים. לְפִיכָךְ צִוּוּ לְהִתְרַחֵק מִן הַכַּעַס עַד שֶׁיַּנְהִיג עַצְמוֹ שֶׁלֹּא יַרְגִּישׁ אֲפִלּוּ לַדְּבָרִים הַמַּכְעִיסִים וְזוֹ הִיא הַדֶּרֶךְ הַטּוֹבָה. וְדֶרֶךְ הַצַּדִּיקִים הֵן עֲלוּבִין וְאֵינָן עוֹלְבִין שׁוֹמְעִים חֶרְפָּתָם וְאֵינָם מְשִׁיבִין עוֹשִׂין מֵאַהֲבָה וּשְׂמֵחִים בְּיִסּוּרִים. וַעֲלֵיהֶם הַכָּתוּב אוֹמֵר (שופטים ה לא) "וְאֹהֲבָיו כְּצֵאת הַשֶּׁמֶשׁ בִּגְבֻרָתוֹ":
(3) And, yet, there are certain tendencies which man is forbidden to follow in the middle-way, but must distance himself from extreme to extreme....
So is anger an extremely evil tendency and it is proper for man to remove himself from it to the other extreme. One should teach himself not to get angry, even over a matter which befits anger. If one desires to engender awe in his children and his household, or in the public, if he be at the head of a community, even if he desire to get angry at them so as to bring them back to the good way, he should only act angry in their presence so as to reprove them, but his disposition must remain calm within himself, even as a man imitates, who is angry when the time calls forth anger but in reality he is not angry. The sages of yore said: "He who yields to anger is as if he worshiped idolatry".1See Nedarim, 22b. G. They also said: "Whosoever yields to anger, if he be a wise man his wisdom leaves him, and if he be a prophet his prophecy leaves him."2Pesahim, 66b. C. Verily the life of irritable persons is no life.3Pesahim, 113a. C. They have, therefore, commanded to be afar from anger, so that one will train himself not to mind even the things which do cause irritation, for such is the good way. The conduct of the just is to take insults but not give insults, hear themselves flouted but make no reply, do their duty as a work of love, and bear affliction cheerfully. Concerning them the Verse says: "But may those that love Him be as the rising of the sun in his might" (Judg. 5.31).