Rav Soloveitchik on Yom Kippur and Forgiveness

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:

Mishnah Yoma 8:9

...Yom Kippur atones for transgressions between a person and God, but for a transgression against one's neighbor, Yom Kippur cannot atone, until he appeases his neighbor. Thus R. Eleazar ben Azariah expounds the text, "From all your sins before the Lord shall ye 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 ye 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.

משנה בבא קמא ח׳:ז׳

(ז) אַף עַל פִּי שֶׁהוּא נוֹתֵן לוֹ, אֵין נִמְחָל לוֹ עַד שֶׁיְּבַקֵּשׁ מִמֶּנּוּ, שֶׁנֶּאֱמַר (בראשית כ) וְעַתָּה הָשֵׁב אֵשֶׁת וְגוֹ'...

Mishnah Bava Kamma 8:7

Even once the thief has given the victim the payment, he will not be forgiven until he seeks pardon from the victim, as it says, "Therefore, restore [Abraham's] wife[—he is a prophet and will intercede for you]" (Genesis 20:7).

Rabbi Y.D. Soloveitchik, Har'rei Kedem 48

The ruling of Rabbi Eleazar ben Azariah regarding the requirement of appeasing one's friend prior to Yom Kippur is different than the general rule of seeking pardon which is stated in the Mishna in Bava Kamma....because for the atonement of Yom Kippur, it is not sufficient that one's friend forgives them, but rather they must additionally appease their friend, which means appeasing them with words, returning their heart to the way that they had felt before the wrongdoing. One must restore the relationship of love and friendship which had existed between them before the sin.

The reason for this is that the atonement of Yom Kippur is one of collective atonement. An individual can only achieve atonement through the community, much like the scapegoat of Yom Kippur is a collective offering. Therefore, in order to unite and unify the community, one must ensure that there is no separation or intervening object which would separate between members of the community.

We might additionally add that some of the mussarists would say that Yom Kippur does not atone for sins between the individual and God until one has received forgiveness from their friend. For the atonement of Yom Kippur is not effected on individual sins, but rather on the person themselves. This is similar to what Rabbi Akiva says at the conclusion of the Mishna in Yoma, "even as a ritual bath purifies the unclean, so does the Holy One purifies Israel." A person cannot purify themselves partially [in the mikvah], or to purify themselves limb by limb; rather, the act of purification in the mikvah is achieved in the instant when the water surrounds the entire body at once. So too is the purification of Yom Kippur, as the Torah states: "Before the Lord you shall be clean"; [Yom Kippur] does not atone partially for ones sins, but rather can only be effective as an entire purification from all of ones sins.