For our blessed master taught (Likkutei Moharan II:60) that lack of rain is caused by wars and murder. And the essence of war is argument. The tikkun, the way to repair an argument, is through fasting, as our blessed master explained at length (Likkutei Moharan 57).
Therefore, we fast when there is a lack of rain, in order to repair the machloket, the argument, which is the war that is the cause of the lack of rain. This is also the essence of the four fast days that we observe in memory of the destruction of the Temple. These also come in order to repair and bring peace, as our sages taught: when there is peace, there is no fasting. Rather, the point of fasting is when there is no peace. And Jerusalem was only destroyed because of baseless hatred, as our blessed sages taught, and we fast in order to repair these arguments and create peace. This is why we fast for any tragic event that occurs, because all suffering (G!d forbid!) comes from argument - since everything that is contrary to what a person desires has the aspect of argument. All the painful suffering (G!d forbid!) are a result of an overflow of dinim, harsh judgement (G!d forbid!), which also bear the aspect of argument. All suffering is connected to sin, and sin is also a type of argument, since the main source of sustenance for the Evil Inclination (and the Sitra Achara) is argument. Therefore, because of an abundance of argument that gives power (G!d forbid!) to the evil Sitra Achara that overcomes holiness, there is an overflow of judgement in the world (G!d forbid!), and this in itself leads to argument, and this brings suffering (G!d forbid!), which one does not desire and is also a form of argument - and in order to repair all this we establish a day of fasting, which comes to repair the machloket, the argument, as we have shown. The important principle is this - we repair all kinds of argument with fasting, as it is said: the more giving charity, the more peace. And the essence of fasting is giving charity, as it is taught: the reward for fasting is actually for the charity given. (Berachot 6b).
מַה שֶּׁמִּתְעַנִּין עַל עֲצִירַת גְּשָׁמִים:
Regarding fasting for the lack of rain.
כִּי כָּתַב רַבֵּנוּ זִכְרוֹנוֹ לִבְרָכָה, (בְּלִקּוּטֵי תִּנְיָנָא סִימָן ס) שֶׁעֲצִירַת גְּשָׁמִים נַעֲשֶׂה עַל-יְדֵי מִלְחָמוֹת וּשְׁפִיכוּת דָּמִים, עַיֵּן שָׁם. וּמִלְחָמוֹת הַיְנוּ מַחֲלֹקֶת. וְתִקּוּן הַמַּחֲלֹקֶת הוּא תַּעֲנִית, כַּמְבֹאָר הֵיטֵב בְּדִבְרֵי רַבֵּנוּ זִכְרוֹנוֹ לִבְרָכָה (בְּסִימָן נז):
For our blessed master taught (Likkutei Moharan II:60) that lack of rain is caused by wars and murder. And the essence of war is argument. The tikkun, the way to repair an argument, is through fasting, as our blessed master explained at length (Likkutei Moharan 57).
וְעַל-כֵּן מִתְעַנִּין עַל עֲצִירַת גְּשָׁמִים לְתַקֵּן הַמַּחֲלֹקֶת, הַיְנוּ מִלְחָמוֹת שֶׁמִּזֶּה נַעֲשֶׂה עֲצִירַת גְּשָׁמִים כַּנַּ"ל. וְזֶהוּ גַּם כֵּן בְּחִינַת הַד' תַּעֲנִיּוֹת שֶׁמִּתְעַנִּין עַל הַחֻרְבָּן. שֶׁהוּא גַּם כֵּן לְתַקֵּן הַשָּׁלוֹם, כְּמוֹ שֶׁאָמְרוּ רַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה, כְּשֶׁיֵּשׁ שָׁלוֹם אֵין צוֹם. שֶׁעִקַּר הַתַּעֲנִית כְּשֶׁאֵין שָׁלוֹם (וְכַמְבֹאָר שָׁם בְּדִבְרֵי רַבֵּנוּ זִכְרוֹנוֹ לִבְרָכָה, עַיֵּן שָׁם). כִּי לֹא חָרְבָה יְרוּשָׁלַיִם אֶלָּא בִּשְׁבִיל שִׂנְאַת חִנָּם, כְּמוֹ שֶׁאָמְרוּ רַבּוֹתֵינוּ זִכְרוֹנָם לִבְרָכָה, וְעַל-כֵּן מִתְעַנִּין לְתַקֵּן זֹאת, כִּי עַל-יְדֵי הַתַּעֲנִית נִתְתַּקֵּן הַמַּחֲלֹקֶת וְנַעֲשֶׂה שָׁלוֹם כַּנַּ"ל. וְכֵן עַל כָּל צָרָה שֶׁלֹּא תָּבוֹא מִתְעַנִּין, כִּי כָּל הַצָּרוֹת וְהַיִּסּוּרִין חַס וְשָׁלוֹם, הֵם בְּחִינַת מַחֲלֹקֶת, כִּי כָּל מַה שֶּׁהוּא נֶגֶד רְצוֹן הָאָדָם הוּא בְּחִינַת מַחֲלֹקֶת, (כְּמוֹ שֶׁמְּבֹאָר שָׁם בְּדִבְרֵי רַבֵּנוּ זִכְרוֹנוֹ לִבְרָכָה הַנַּ"ל). כִּי הַצָּרוֹת חַס וְשָׁלוֹם, הֵם עַל-יְדֵי הִתְגַּבְּרוּת הַדִּינִים חַס וְשָׁלוֹם, שֶׁהֵם בְּחִינַת מַחֲלֹקֶת, דְּהַיְנוּ שֶׁאֵין נִכְלָל שְׂמֹאל בְּיָמִין חַס וְשָׁלוֹם, שֶׁזֶּה בְּחִינַת מַחֲלֹקֶת, בְּחִינַת דִּינִים. כִּי אֵין יִסּוּרִין בְּלָא עָוֹן וְהֶעָוֹן הוּא בְּחִינַת מַחֲלֹקֶת, כִּי עִקַּר יְנִיקַת הַסִּטְרָא אָחֳרָא וְהַיֵּצֶר הָרָע הוּא מִמַּחֲלוֹקוֹת, (כַּמְבֹאָר בְּדִבְרֵי רַבֵּנוּ זִכְרוֹנוֹ לִבְרָכָה). נִמְצָא, שֶׁעַל-יְדֵי הָעֲווֹנוֹת שֶׁפָּגַם הַמַּחֲלֹקֶת שֶׁנָּתַן כֹּחַ חַס וְשָׁלוֹם, לְהַסִּטְרָא אָחֳרָא הַחוֹלֶקֶת עַל הַקְּדֻשָּׁה, עַל-כֵּן נִתְעוֹרְרוּ עָלָיו דִּינִים חַס וְשָׁלוֹם, שֶׁהֵם בְּחִינַת מַחֲלֹקֶת וּמִשָּׁם בָּאִים הַצָּרוֹת חַס וְשָׁלוֹם, שֶׁהֵם כְּנֶגֶד רְצוֹנוֹ, בְּחִינַת מַחֲלוֹקוֹת, וּלְתַקֵּן זֹאת גּוֹזְרִין תַּעֲנִית שֶׁהִיא תִּקּוּן הַמַּחֲלֹקֶת כַּנַּ"ל, כִּי הַכְּלָל שֶׁכְּנֶגֶד כָּל מִינֵי מַחֲלֹקֶת הַתִּקּוּן הוּא תַּעֲנִית בִּבְחִינַת מַרְבֶּה צְדָקָה מרבה שָׁלוֹם. וְעִקַּר הַתַּעֲנִית הוּא הַצְּדָקָה, כִּי אַגְרָא דְּתַעֲנִיתָא צִדְקְתָא, עַיֵּן שָׁם:
Therefore, we fast when there is a lack of rain, in order to repair the machloket, the argument, which is the war that is the cause of the lack of rain. This is also the essence of the four fast days that we observe in memory of the destruction of the Temple. These also come in order to repair and bring peace, as our sages taught: when there is peace, there is no fasting. Rather, the point of fasting is when there is no peace. And Jerusalem was only destroyed because of baseless hatred, as our blessed sages taught, and we fast in order to repair these arguments and create peace. This is why we fast for any tragic event that occurs, because all suffering (G!d forbid!) comes from argument - since everything that is contrary to what a person desires has the aspect of argument. All the painful suffering (G!d forbid!) are a result of an overflow of dinim, harsh judgement (G!d forbid!), which also bear the aspect of argument. All suffering is connected to sin, and sin is also a type of argument, since the main source of sustenance for the Evil Inclination (and the Sitra Achara) is argument. Therefore, because of an abundance of argument that gives power (G!d forbid!) to the evil Sitra Achara that overcomes holiness, there is an overflow of judgement in the world (G!d forbid!), and this in itself leads to argument, and this brings suffering (G!d forbid!), which one does not desire and is also a form of argument - and in order to repair all this we establish a day of fasting, which comes to repair the machloket, the argument, as we have shown. The important principle is this - we repair all kinds of argument with fasting, as it is said: the more giving charity, the more peace. And the essence of fasting is giving charity, as it is taught: the reward for fasting is actually for the charity given. (Berachot 6b).