Мусар к Вайикра 2:1

ומן המקדש לא יצא . Every person must make of himself a servant of G–d, must sanctify himself so as to come as close to the sanctity of the High Priest as is possible. He should practice some solitude and avoid emerging from this communion with G–d to the extent his circumstances allow. He must be concerned that no blemish, physical or spiritual, should attach to him. His striving must be that he himself should qualify as an offering to G–d. Once he endeavors to do all this is he is considered קדוש לה'.

Our sages added that the animal first has to be thrown to the ground forcefully as a symbol of man having thrown down his own person, thereby confessing that he himself is guilty of death by stoning. When the animal is slaughtered this is equivalent to the owner killing himself suggesting that he is guilty of the two death penalties: death by the sword and by hanging. (There is a momentary feeling of choking experienced by the animal before the knife slices through its throat). When the animal is burned on the altar, this symbolizes the fourth kind of death penalty, death by burning. The owner of the animal recites a confession and G–d accepts it. The priest must also see to it that at the time when he sprinkles the animal's blood on the altar the man or woman for whom he performs this service should observe what he is doing. The priest is not himself allowed to look directly at a woman while he performs service in the precincts of the Temple; the copper laver used in the Temple was made of the mirrors the Jewish women used in Egypt when they prettied themselves for their husbands; when the priest offers a sin-offering owned by a woman he looks at this copper laver and sees her reflection in it. This has been explained by the Rekanati. The rule we learn from all that we have described above is that the person who offers the sacrifice should regard himself as being sacrificed. He is then fulfilling (2,1): ונפש כי תקריב קרבן מנחה "When a person sacrifices (himself) as a gift-offering".

From what I have explained you will understand that by means of the (animal) sacrifice man's "lower" will is elevated and thereby able to approach G–d's "higher" will. G–d's will in turn is also able to relate more closely to man's "lower" will. It is incumbent on the lowly to subdue his will by means of the sacrifice, so that man's soul, נפש, will identify with the נפש of the animal he offers up. When he does this the Torah will consider his sacrifice as if he had sacrificed his own נפש, his own life. When the priest offers the sacrifice, his נפש "sticks" to the נפש on the Celestial Altar in the first instance, and then proceeds to still higher regions. When that process is complete the priest is called מלאך. This is what Malachi 2,7 has in mind when he describes the function of the priest as מלאך ה' צבאות הוא.