Sefer HaChinuch ספר החינוך

The commandment of the service of Yom Kippur: That the high priest do all the procedure of Yom Kippur, with the order of the sacrifices, the confessions, the sending away of the goat and the rest of the service, as it is written in the section of the Torah — as it is stated (Leviticus 16:3), “With this shall Aharon enter the Holy, etc.” until the end of the section.

It is from the roots of the commandment that it was from the kindnesses of God towards His creatures to fix one day in the year for the atonement of sins, with the repentance that they repent. As if the iniquities of the creatures would accumulate year by year, their measure would be full at the end of two or three years or more, and the world would be liable for destruction. And therefore He, blessed be He, saw in His wisdom — for the survival of the world — to fix one day a year for the atonement of sins for penitents. And from the beginning of the creation of the world (Bereshit Rabbah 2:3), He designated it and sanctified it for this. And since God, blessed be He, designated that day for atonement, the day was sanctified and received the power of merit from Him, may He be elevated, to the point that it aids atonement. And this is [the meaning] of their, may their memory be blessed, saying in many places (Yoma 85b), “Yom Kippur atones” — meaning to say that there is power in Yom Kippur, itself, to atone for light sins.

From the laws of the commandment is that which they, may their memory be blessed, said (Yoma 70a) that on that day they would offer the daily morning sacrifice and the daily afternoon sacrifice according to the order of each and every day. And they would offer the additional (musaf) sacrifice of the day — a bull and a ram and seven sheep, all burnt-offerings, and a goat for a sin-offering, and it was processed outside, and eaten in the evening. And they would further offer beyond this, a young bull for a sin-offering, and it was burnt; a ram for a burnt-offering — and they were both of the high priest’s; and the ram that came from that of the community that is stated in this section, and it is the ram stated in the Book of Numbers as part of the additional service, and it is called the “ram of the people.” And they would also bring two male goats from that of the community — one they would offer as a sin-offering and it was burnt, and the second was the goat sent away (the scapegoat). All of the beasts that would be offered on the day of the fast — besides the goat sent away, which was not offered — come out to fifteen: two daily ones; a bull; two rams; seven sheep — all of them burnt-offerings; two goats for sin-offerings, one was processed outside and eaten in the evening, and the second was processed inside and burned; and also a young bull for a sin-offering. All fifteen of the beasts that were offered on this day were only [offered] by the high priest anointed by the anointing oil or who [simply] had more [officiating] garments. And if it was Shabbat, only the priest would offer the additional [offering]. And likewise the other procedures of the day, such as the incense of every day and the arrangement of the lights — all was [done] by a married high priest, as it is stated (Leviticus 16:11), “and he shall atone for himself and for his home” — [the meaning of] his home is his wife.

And the rest of all of the procedures: the change of garments from the white garments to the gold garments, and from the gold garments to the white garments; the five immersions that he would immerse on this day; the ten times he would sanctify his hands and feet; the matter of separating that they would separate him seven days before the fast day; the honor that they would [show] him; the confessions that he would say; and all the rest of the laws of this day — it is all in the tractate that is built upon it, and that is Tractate Yoma. (See Mishneh Torah, Laws of Service on the Day of Atonement 1.)

And all of this commandment is practiced at the time of the [Temple]. And now that — due to our iniquities — we have neither a Temple nor a high priest, neither serving garments nor sacrifices, all of Israel has been accustomed to serve on this day though our prayers and supplications. And [it is] as it is written (Hoshea 14:3), “and [instead of] bulls, we shall pay [the offering of] our lips.”