"You shall afflict your soul on the ninth of the month [of Tishrei] in the evening, from evening to evening you shall rest" (Vayikra 23:32). As Yom Kippur begins on the tenth of Tishrei--"but on the tenth of this seventh month, it is Yom HaKippurim" (23:27)--the Torah's phraseology is rather strange. Why say "the ninth in the evening" if you mean the tenth? This unusual wording led Rabbi Yishmael (Rosh Hashanah 9a) to teach that we must "add from the secular to the holy", both at the start and the end of Yom Kippur.
The kohen gadol performed vidui, confession, three times on Yom Kippur. The first two were done using his own personal bull offering, asking for forgiveness for the sins of his family and for his fellow kohanim. The third vidui, for the sins of the people of Israel, was done with the shair hamistalech, the "scapegoat" that would then be led off to the desert and hurled off a mountain.
The kohen gadol had a hard day of work on Yom Kippur. The avodah, the special Yom Kippur Temple service, was intricate and difficult, and had to be performed after the kohen gadol was forced to stay up all night. He was kept up to avoid the possibility of a seminal emission, which would disqualify him from working on Yom Kippur. The Gemara relates how the mikarei Yerushalayim, the important people of Jerusalem, would also stay up making noise through the night, to make it difficult for the high priest to doze off (Yoma 19b).
“And he shall atone for himself and for his household” (Vayikra 16:6). The Rabbis derive from this verse that the kohen gadol, in order to effect atonement, must be married. What if the kohen gadol should suddenly become single? What would happen if his wife were to die suddenly, just prior to Yom Kippur? The Sages argue that we need not worry about such.
In trying to develop the potential of man, the Mussar movement developed two different approaches to the sinning of man. One school of thought, exemplified by the approach developed in Novordak, stressed the lowliness of man--our propensity to sin, our animalistic tendencies and our need for repentance. The second school of thought, represented by Slobodka, stressed the greatness of man--created in the image of G-d, tasked with building up the world, and with so much to offer. How could one who is so great allow themselves to sin?
Man, unique amongst all creations, was blessed by G-d with a soul. We are not just physical creations, doomed to death in due course, but spiritual beings whose souls can live forever.
“Seek out G-d when He can be found, call upon Him when He is near” (Isaiah 55:6). Our Sages interpret this verse as referring to the Aseret Yemei Teshuva, the ten days of repentance, which begin on Rosh Hashanah and end with the conclusion of Yom Kippur. This is the season when G-d is closer to us and thus our prayers stand a “better chance” of success.