1. Christ who accomplished the eternal Atonement at once (Lev 16:27-30)
    Heb 10:1-10, 15-18, Heb 7:27

In the Old Testament, the people of Israel received forgiveness from God every year on the Day of Atonement. (Lev 16:27-30)

Lev 16:27 And the bullock for the sin offering, and the goat for the sin offering, whose blood was brought in to make atonement in the holy place, shall one carry forth without the camp; and they shall burn in the fire their skins, and their flesh, and their dung.
28 And he that burneth them shall wash his clothes, and bathe his flesh in water, and afterward he shall come into the camp.
29 And this shall be a statute for ever unto you: that in the seventh month, on the tenth day of the month, ye shall afflict your souls, and do no work at all, whether it be one of your own country, or a stranger that sojourneth among you:
30 For on that day shall the priest make an atonement for you, to cleanse you, that ye may be clean from all your sins before the Lord.

We cannot be made perfect through the annual sacrifices offered in the Old Testament. The sacrifice offered in the Old Testament is a shadow of the coming Christ. When Jesus came to this earth as the Christ, he offered his body to God once for all to forgive our sins. (Heb 10:1-10,15-18, Heb 7:27)

Heb 10:1 For the law having a shadow of good things to come, and not the very image of the things, can never with those sacrifices which they offered year by year continually make the comers thereunto perfect.
2 For then would they not have ceased to be offered? because that the worshippers once purged should have had no more conscience of sins.
3 But in those sacrifices there is a remembrance again made of sins every year.
4 For it is not possible that the blood of bulls and of goats should take away sins.
5 Wherefore when he cometh into the world, he saith, Sacrifice and offering thou wouldest not, but a body hast thou prepared me:
6 In burnt offerings and sacrifices for sin thou hast had no pleasure.
7 Then said I, Lo, I come (in the volume of the book it is written of me,) to do thy will, O God.
8 Above when he said, Sacrifice and offering and burnt offerings and offering for sin thou wouldest not, neither hadst pleasure therein; which are offered by the law;
9 Then said he, Lo, I come to do thy will, O God. He taketh away the first, that he may establish the second.
10 By the which will we are sanctified through the offering of the body of Jesus Christ once for all.
15 Whereof the Holy Ghost also is a witness to us: for after that he had said before,
16 This is the covenant that I will make with them after those days, saith the Lord, I will put my laws into their hearts, and in their minds will I write them;
17 And their sins and iniquities will I remember no more.
18 Now where remission of these is, there is no more offering for sin.

Heb 7:27 Who needeth not daily, as those high priests, to offer up sacrifice, first for his own sins, and then for the people’s: for this he did once, when he offered up himself.