עֲבֵרוֹת שֶׁבֵּין אָדָם לַמָּקוֹם, יוֹם הַכִּפּוּרִים מְכַפֵּר. עֲבֵרוֹת שֶׁבֵּין אָדָם לַחֲבֵרוֹ, אֵין יוֹם הַכִּפּוּרִים מְכַפֵּר, עַד שֶׁיְּרַצֶּה אֶת חֲבֵרוֹ. אֶת זוֹ דָּרַשׁ רַבִּי אֶלְעָזָר בֶּן עֲזַרְיָה, מִכֹּל חַטֹּאתֵיכֶם לִפְנֵי יְיָ תִּטְהָרוּ (ויקרא טז), עֲבֵרוֹת שֶׁבֵּין אָדָם לַמָּקוֹם, יוֹם הַכִּפּוּרִים מְכַפֵּר. עֲבֵרוֹת שֶׁבֵּין אָדָם לַחֲבֵרוֹ, אֵין יוֹם הַכִּפּוּרִים מְכַפֵּר, עַד שֶׁיְּרַצֶּה אֶת חֲבֵרוֹ. אָמַר רַבִּי עֲקִיבָא, אַשְׁרֵיכֶם יִשְׂרָאֵל, לִפְנֵי מִי אַתֶּם מִטַּהֲרִין, וּמִי מְטַהֵר אֶתְכֶם, אֲבִיכֶם שֶׁבַּשָּׁמַיִם, שֶׁנֶּאֱמַר (יחזקאל לו), וְזָרַקְתִּי עֲלֵיכֶם מַיִם טְהוֹרִים וּטְהַרְתֶּם. וְאוֹמֵר (ירמיה יז), מִקְוֵה יִשְׂרָאֵל יְיָ, מַה מִּקְוֶה מְטַהֵר אֶת הַטְּמֵאִים, אַף הַקָּדוֹשׁ בָּרוּךְ הוּא מְטַהֵר אֶת יִשְׂרָאֵל:
Yom Kippur atones for transgressions between a person and God, but for a transgression against one’s neighbor, Yom Kipur cannot atone, until he appeases his neighbor. Thus R. Eleazar ben Azariah expounds the text, “From all your sins before the Lord shall you be clean”: For transgressions between a person and God, Yom Kippur atones, for transgressions against one’s neighbor, Yom Kippur cannot atone, until he appeases his neighbor. R. Akiva says, Happy are you, Israel! Before whom are you purified, and who purifies you [of your transgressions]? Your Father Who is in heaven. For it is said, “Then will I sprinkle clean water upon you, and you shall be clean”; and it is also said, “The ritual bath [lit. Hope] of Israel is the Lord”; even as a ritual bath purifies the unclean, so does the Holy One, Blessed be He, purify Israel.
What has the part about YK not atoning for Bein Adam La-chaveiro have to do with the latter part about Hashem purifying us?
The Medrash says:
הלא נדב ואביהוא בניסן מתו ולמה נסמכה מיתתן לפרשת יוכ”פ לומר לך שמיתת צדיקים מכפרת ומנין שיוה”כ מכפר? שנאמר לפני ד’ תטהרו.
Nadav and Avihu died in Nissan so why is their death mentioned next to the parsha of Yom kippur? To tell us that the death of Tzadikim atones just like Yom Kippur. And how do we know that Yom Kippur atones? It says לפני ה’ תטהרו.
Isn’t that a WEIRD question “How do we know that Yom Kippur atones”??? Like, any kid knows that??!!
Now the Gemara says that YK atones only for Bein Adam La-makom so it would seem that the same applies to the death of Tzadikim. But the Gemara in Shabbos  says that if someone cries over the demise of a good person, all of his sins are atoned for. This implies that the death of Tzadikim is GREATER than YK! Could it be??
The primary teshuva is to clearly regret the past and accept upon himself to act properly in the future. Then he will have proper love of Hashem and enter the king’s palace. The Gemara says that R’ Shimon would expound every time the Torah says the word “את” to include something new. When he reached the pasuk “את ה’ אלקיך תירא” [one must fear Hashem] he stopped! How can one equate ANYONE to Hashem??
Everyone asks: Earlier the Torah says “ואהבת את ה’ אלקיך” [one must love Hashem]. Why didn’t he have a problem with the “את” over there??!
The answer may be that there is a special mitzva to “latch on” to Talmidei Chachomim that is derived from the pasuk “ובו תדבק”. So the mitzva of loving Hashem INCLUDES Torah scholars!!:-)! But fear? That is for G-d alone.
If you love Talmidei Chochomim you will also be careful to beg them for forgiveness if you offended them [and thus do proper teshuva]. This love will bring you to love Hashem. For why do we love all Jews and particularly Talmidei Chachomim, if not for the fact that they are G-d’s creations!! So teshuva – returning to Hashem – starts with love of all Talmidei Chachomim.
When we cry over the loss of a Talmid Chochom all of our sins are forgiven because this is an expression of our love of G-d.
So the Mishna says that there is no forgiveness if we don’t first ask other Jews [and particularly Talmidei Chachomim who deserve the most love] for forgiveness. When we do that then Hashem will wash off our sins. That explains the latter part of the Mishna that says לפני מי אתם מטהרים ומי מטהר אתכם. Rabbeinu Ephraim Alankava [a Rishon who wrote a commentary on the Chumash] says that in the zchus that Avraham said ורחצו – wash, we merited the pasuk וזרקתי עליכם מים טהורים. The Mishna is teaching that if we “wash” ourselves then Hashem will wash us.
The question of the Medrash is how do we know that YK atones COMPLETELY like the death of Tzadikim.
[עפ”י אורי וישעי פ’ נ”ט]