Day Of Purification
Though we generally associate Yom Kippur with atonement, the Torah defines taharah (purification) as the day’s goal:
On Yom Kippur, Hashem atones for our sins in order to purify us.
The purification relates to both the Beit HaMikdash and the Jewish People.  This is why the Yom Kippur Torah readings detail purification of both the Beit Mikdash (in the morning reading, Vayikra Perek 16 and the Jewish people (in the afternoon reading. ).
The Damage Of Sin
We are, of course, familiar with how the concept of taharah applies to the context of ritual purity. We are not as familiar with its relevance to the non-ritual sense. What does taharah mean in a personal, spiritual context?
Understanding spiritual purity hinges on appreciating the impact that sin has upon us. Sin is not just wrong and damning; it also defiles our soul and spirit. Mitzvah fulfillment sanctifies; transgression defiles. Rav Chaim Volozhin [Nefesh Hachayim 2:8] compared sin to the consumption of unhealthy food. Just as the latter damages us physically, so the former taints us spiritually. 
David Hamelech links taharah to the heart and spirit. The Shaarei Teshuvah [1:9] and Mesilat Yesharim [Perek 17 — Midat Hataharah] explain that taharah hinges upon motivation—the why of what we do (beyond what we do). Tahor people are motivated by their wisdom and fear of Hashem, not their base desires.
Taharah’s focus on the heart helps us understand why the Rambam [Teshuvah 7:3] sees teshuvah as addressing not just sin, but also improper character traits. Purification is not just about correcting action, but, mainly, about personal improvement.
The pesukim we have seen—about taharah in general (Tehillim) and about Yom Kippur specifically (Vayikra)—describe Hashem purifying us. This explains the request we make in each of our Shabbat and yom tov prayers:
We ask Hashem to purify our hearts so we can serve him in earnest.
The conclusion of the Yom Kippur pasuk—the word “tit’haru”— commands us to purify ourselves.  The Kohen Gadol used this word at the height of the Yom Kippur atonement service to remind those in the Mikdash of their responsibility to purify themselves. His verbal response to those who prostrated themselves upon his utterance of Hashem’s (most) sacred name was “titaharu.” He emphasized that his avodah alone was not enough. Each person needed to purify himself.
When we make the effort to purify ourselves, Hashem completes the process for us. Shaarei Teshuvah [2:14] summarizes the process this way: 
“The Torah commands us to purify ourselves through teshuvah before Hashem so He can purify us through His atonement.”
How We Purify Ourselves
Most of us are familiar with the process and stages of teshuvah. But how do we purify ourselves? The mishnah at the end of Masechet Yoma gives us direction by describing Hashem Himself as the proverbial mikveh we are meant to purify ourselves in.  Hashem is totally disconnected from all sin and defilement. By reconnecting with Him, we return to a natural state of purity. Like the Kohen Gadol who immerses himself ten times over the course of Yom Kippur and then enters the holy cloud (created by the ketoret) within the holiest part of Hashem’s sanctuary, we are also ‘immerse ourselves’ within our connection to Hashem.
After elaborating on this notion, the Maharal [Kitvei HaMaharal, D’rush L’Shabbat Shuvah ] emphasizes that, like immersion in an actual mikveh, we only achieve taharah by connecting (through committing) ourselves fully to Hashem. Even a small chatzizah (separation) renders the “immersion” completely meaningless.
Returning To Ourselves
On a deeper (yet simpler) level, our return to Hashem is essentially a return to our natural, true selves.
This applies on two levels. Firstly, because our soul emanates from Hashem [Bereishit 2:7 with Rashi and Ramban], we need look no further than inside ourselves to find His holiness. As the Torah writes, “It is not in the sky or beyond the seas, but in our own mouths and hearts. [Devarim 30: 11-14]
Secondly, because our soul is of G-dly origin, our reconnection with Hashem ultimately reconnects us to our true selves. For this reason, Rav Kook explained that our return to Hashem regenerates our natural, holy soul. 
We find Hashem by looking inside ourselves and find our true selves by reconnected with Him.
Though taharah is always an important goal, Yom Kippur is the time when this self-purification is most possible and impactful. Let’s make sure to take full advantage of the opportunity
Rabbi Reuven Taragin is the dean of overseas students at Yeshivat HaKotel.
1. This explains the centrality of purity to Yom Kippur ritual, which can be seen in the need for tevilah (ten times by the Kohen Gadol and customarily performed by all males before Yom Kippur) and the custom to wear white.
2. Perek 18 describes sexual sins as defiling us in pesukim 20, 23, and 24. The next pesukim (25–30) describe how these sins defile the land as well. See also Bamidbar 35, which depicts murder as defiling the land.
3. In addition to the damage caused on the spiritual plane, the Gemara in Yoma (39a) depicts how sin damages even one’s intellectual capacity (see also Or HaChayim to Vayikra 11:43)
4. See Shaarei Teshuvah (2:14, 4:17), who sees this phrase as the basis of the unique chiyuv to do teshuvah on Yom Kippur
5. The duality of Hashem purifying us and our self-purification is presented by the Mishnah 85b. See also Yoma 39b
6. See Rambam Mikvaot (11:12), who also uses immersion in a mikvah as a model for personal purification.
7. Orot Hateshuvah 15:10. The morning prayer of Elokai Neshama builds off this idea.