Yom Kippur saves the average person

אי' במדרש וישעי הוא ביוה"כ דעיקר הישועה צריכים הבינונים.

It is brought in the Midrash that "and my salvation" (Tehillim 27:1) refers to Yom Kippur, for it is the beinonim (those who are neither fully righteous nor wicked) who are most in need of yeshuah (salvation).

The Sefas Emes opens by noting that the verse "Hashem is my light and my salvation" is read on the Yamim Nora'im, and the "salvation" part hints at Yom Kippur - the day whose deliverance is needed above all by the average person, who hangs in the balance.

דכתי' צדקתך הוא צדיקים גמורים.

For it is written, "Your righteousness" (Tehillim 36:7) - this refers to the complete tzaddikim.

The verse describing Hashem's righteousness as towering "like the mighty mountains" speaks of the perfectly righteous, who stand on firm and elevated ground and need no special rescue.

משפטיך תהום רבה הרשעים.

"Your judgments are a great deep" (Tehillim 36:7) - this refers to the wicked.

The resha'im are likened to the "great deep," sunk in the depths and subject to strict din (judgment), beyond the reach of the day's salvation.

אדם ובהמה הם הבינונים זה וזה שופטן.

"Man and beast" (Tehillim 36:7) - these are the beinonim, whom both this trait and that one judge.

The middle of the verse, "man and beast You save, Hashem," corresponds to the average person, who has within him both an elevated human side ("adam") and an animalistic side ("behemah"). Such a person is pulled and judged by both his righteous and wicked tendencies.

להם תושיע ה' ביוה"כ:

It is for them that "You save, Hashem" - on Yom Kippur.

Precisely because the beinoni is suspended between his two natures, the salvation of Yom Kippur is directed to him: Hashem tips the scale toward life and reaches down to rescue the one who is neither wholly tzaddik nor wholly rasha.

Summary: Reading the verse "man and beast You save, Hashem," the Sefas Emes teaches that Yom Kippur's salvation is aimed at the beinoni - the average person who contains both a holy human dimension and an animal dimension - for the perfectly righteous need no rescue and the wicked lie beyond it, while the one in between is the very object of Hashem's saving on this day.