Before us is Mishnah 9, the final Mishnah of Maseches Yoma, containing several closing thoughts on the atonement of Yom Kippur.
"Echteh ve'ashuv" - I will sin and then repent:
"Ha'omer echteh ve'ashuv, echteh ve'ashuv - ein maspikin beyado la'asos teshuvah" - one who says, "I will sin and I will repent, I will sin and I will repent," is not given the ability to repent. Heaven does not assist him, and he will not find within himself the strength to do teshuvah.
"Echteh veYom haKippurim yechaper - ein Yom haKippurim mechaper" - one who says, "I will sin and Yom Kippur will atone," Yom Kippur does not atone for him. The commentators explain that this does not mean that Yom Kippur lacks the power to atone in and of itself, but rather that such a person will not merit to do the proper teshuvah that is required in order for Yom Kippur to atone.
Sins between a person and God, and sins between a person and his fellow:
For sins between a person and God, Yom Kippur atones. But for sins between a person and his fellow, Yom Kippur does not atone until he appeases his fellow and receives his forgiveness. Every sin that a person commits against his fellow also contains an element of a sin against God, but appeasing one's fellow and obtaining his forgiveness are a prerequisite: only afterward can a person merit forgiveness from God and do teshuvah properly.
The exposition of Rabbi Elazar ben Azaryah:
Rabbi Elazar ben Azaryah expounded the verse stated regarding Yom Kippur: "Mikol chatoseichem lifnei Hashem tit'haru" - from all your sins before Hashem shall you be cleansed. From the words "before Hashem" he learned that sins between a person and God, which are between him and Hashem alone, are cleansed through Yom Kippur; but for sins between a person and his fellow, Yom Kippur does not atone until he appeases his fellow and gains his consent and forgiveness.
The words of Rabbi Akiva that conclude the tractate:
Rabbi Akiva said: "Ashreichem Yisrael, lifnei mi atem mitaharin umi metaher eschem - Avichem shebaShamayim" - fortunate are you, Israel; before whom are you cleansed, and who cleanses you? Your Father in Heaven. He brought two verses for this: "Vezarakti aleichem mayim tehorim utehartem" - and I will sprinkle upon you pure waters and you shall be cleansed, and "Mikveh Yisrael Hashem" - the hope (mikvah) of Israel is Hashem. The Holy One Himself is the mikvah that purifies Israel, and just as a mikvah purifies those who are tamei, so too the Holy One purifies the Jewish people.
In summary: in this Mishnah we learned that one who sins while relying on repentance, or while relying on the atonement of Yom Kippur, does not merit Heavenly assistance to repent properly; that Yom Kippur atones for sins between a person and God, while sins between a person and his fellow require appeasing one's fellow and receiving his forgiveness, as Rabbi Elazar ben Azaryah expounded from the words "before Hashem shall you be cleansed"; and, in Rabbi Akiva's concluding words, that the Holy One Himself is the mikvah of Israel who purifies His people.
With this, Maseches Yoma comes to an end. I hope you will join us as we continue learning.