הריני מקבל עלי
את מצות הברא
ואהבת לרעך כמוך
לרעך כמוך!
A Kavvanah Before Prayer
I hereby accept upon myself
the commandment of The Creator
to love my neighbor as myself!
(יז) לֹֽא־תִשְׂנָ֥א אֶת־אָחִ֖יךָ בִּלְבָבֶ֑ךָ הוֹכֵ֤חַ תּוֹכִ֙יחַ֙ אֶת־עֲמִיתֶ֔ךָ וְלֹא־תִשָּׂ֥א עָלָ֖יו חֵֽטְא׃ (יח) לֹֽא־תִקֹּ֤ם וְלֹֽא־תִטֹּר֙ אֶת־בְּנֵ֣י עַמֶּ֔ךָ וְאָֽהַבְתָּ֥ לְרֵעֲךָ֖ כָּמ֑וֹךָ אֲנִ֖י ה':
(17) You shall not hate your brother in your heart; you shall rebuke your fellow, and do not bear a sin because of him. (18) You shall not take revenge, and you shall not bear grudge against the members of your people, you shall love your companion as yourself: I am God.
מקדש ראשון מפני מה חרב מפני ג' דברים שהיו בו ע"ז וגלוי עריות ושפיכות דמים
For what reason was the first Temple destroyed? Because of three sins which were committed there: idolatry, sexual immorality, and murder.
But the second Temple, where they were immersed in Torah, the commandments, and acts of kindness, why was it destroyed? Because there was baseless hatred there. This demonstrates that baseless hatred is equal to the three cardinal sins (idolatry, sexual immorality, and murder).
תנא דבי אליהו רבה כ"ו, ו'
כך אמר להם הקב"ה לישראל. בניי. כלום חיסרתי מכם. מה אני מבקש מכם. הא איני מבקש אלא כדי שתהיו אוהבין זה את זה. ותהיו מכבדין זה את זה. ותהיו יראין זה מזה.
Tana d'Bei Eliyahu Rabbah 26:6
This is what the Holy One said to Israel: My children, what do i seek from you? I seek no more than that you have love for one another, and respect for one another; and that you have reverence for one another
Imrei Pinchas HaShalem
“[Rabbi Pinchas of Koretz] spoke at length about the love of Israel, [saying] that one must love every individual of Israel, and when you sees that someone hates you, you must love them more, for Israel is a Throne for the Shekhina [Presence of G-d] and for holiness. When - G-d forbid!—there is a rift between them, as it were, a hole, an empty space, is created in the Throne, and then, in this way, holiness falls into the
[power] of the ‘shells’ kelippot [of evil]—G-d forbid! Therefore one must love others a great deal in order to close up the empty space [in the Throne]. Let no one say: ‘I cannot enter into this quality’ for this is a lie. Certainly, by oneself, one may not be able to [do this], but with the help of the blessed G-d, one can attain to the service of the divine [and thus to the love of Israel]. This quality can bring the Messiah, i.e. by loving every person, even the completely wicked, for hatred without cause destroyed our Temple, and because of our sins, it is still ‘dancing’ among us. Therefore, one must strive to bring oneself to this quality”
Ha Rav Menachem Mendel Schneerson z"l (Lubavicher Rebbe)
Brotherly love and harmony begin with the "great axiom of the Torah," namely, "Love your neighbor as yourself." As my father-in-law, the Rebbe would say: Love of a fellow Jew should even extend to a Jew on the other side of the world - even to someone you have never seen.
And when you have an opportunity to do a favor — materially or spiritually — for this Jew, you should do it freely and with a joyful heart.… When there is harmony amongst Jews (in addition to the harmony of a Jewish home — and preceding that, a Jew’s inward harmony — between his two inclinations), then there is peace and harmony in the entire world — especially, "peace in the land" — the Land of Israel.