Our prophets tell us: "Seek HaShem when He can be found. Call to Him as He is near." Our sages tell us - "These are the ten days between Rosh HaShanah and Yom Kippur." Although HaShem is always among us, there are times that He listens to our prayers more closely. And therefore, we set these days apart to pray more and to do teshuvah. We call these days Aseres Yimay Teshuvah - the Ten Days of Repentance.

But wait a minute. Our sages said: "Ten days between Rosh HaShanah and Yom Kippur." We don't need a calculator to figure out that there are only seven days between Rosh HaShanah and Yom Kippur. Since we call these days "the ten days of repentance," we are obviously including Rosh HaShanah and Yom Kippur.

Rosh HaShanah and Yom Kippur are included in these ten days, because an important part of these holidays is teshuvah, returning to HaShem. But then why did our Sages say: "between Rosh HaShanah and Yom Kippur." When we say "between," we usually do not include the beginning and the end. If Rosh HaShanah and Yom Kippur are part of these ten days, what is the beginning and what is the end?

On Rosh HaShanah, we are doing teshuvah, but we have a special task that makes us reach even deeper than teshuvah. On Rosh HaShanah, we proclaim HaShem as King of the Universe. This is the beginning for these ten days.

Yom Kippur is the last of the ten days of teshuvah. On this holy day, we are also doing teshuvah. But again there is something on this day that is deeper than teshuvah.

What would happen on Yom Kippur in the Beis HaMikdash? The kohen gadol would enter the Kodesh HaKodeshim, the Holy of Holies. No one else would be with him. He would stand alone, before the Aron HaKodesh, the ark where HaShem's holiness rests. This level of closeness with HaShem is what is most important about Yom Kippur.

Even today, although the Beis HaMikdash has not yet been rebuilt, every Jew can also share this special bond of closeness with HaShem. After we daven all day, we come to the final prayer of Neilah. Neilah means "locking." At the end of a full day of fasting and davening, a Jew comes very close to HaShem. He is locked in, together with HaShem, like the kohen gadol in the Kodesh HaKedoshim. This special closeness is the end-point of the Ten Days of Teshuvah.

(Adapted from Likkutei Sichos, Vol. IV, Yom Kippur)