1 On the eighth day Moses called Aaron and his sons and the elders of Israel, 2 and he said to Aaron, “Take for yourself a bull calf for a sin offering and a ram for a burnt offering, both without blemish, and offer them before the Lord. 3 And say to the people of Israel, ‘Take a male goat for a sin offering, and a calf and a lamb, both a year old without blemish, for a burnt offering, 4 and an ox and a ram for peace offerings, to sacrifice before the Lord, and a grain offering mixed with oil, for today the Lord will appear to you.’” 5 And they brought what Moses commanded in front of the tent of meeting, and all the congregation drew near and stood before the Lord. 6 And Moses said, “This is the thing that the Lord commanded you to do, that the glory of the Lord may appear to you.” 7 Then Moses said to Aaron, “Draw near to the altar and offer your sin offering and your burnt offering and make atonement for yourself and for the people, and bring the offering of the people and make atonement for them, as the Lord has commanded.”
-So the priests needed a burnt + sin offering at the conclusion of being consecrated and the people needed a sin + burnt + peace + grain offering. The sin offering was for Aaron himself and the burnt offering was done on behalf of the people. The priests have been consecrated before God but the people now must tie themselves to the priests. Each side has a burnt offering which again means “dedication” and each side must cover their sins in a sin offering. Now the people must submit a peace offering to make a “treaty” or deal with the priests and the grain offering is used to celebrate this process and the Lord’s coming appearance.
8 So Aaron drew near to the altar and killed the calf of the sin offering, which was for himself. 9 And the sons of Aaron presented the blood to him, and he dipped his finger in the blood and put it on the horns of the altar and poured out the blood at the base of the altar. 10 But the fat and the kidneys and the long lobe of the liver from the sin offering he burned on the altar, as the Lord commanded Moses. 11 The flesh and the skin he burned up with fire outside the camp. 12 Then he killed the burnt offering, and Aaron’s sons handed him the blood, and he threw it against the sides of the altar. 13 And they handed the burnt offering to him, piece by piece, and the head, and he burned them on the altar. 14 And he washed the entrails and the legs and burned them with the burnt offering on the altar. 15 Then he presented the people’s offering and took the goat of the sin offering that was for the people and killed it and offered it as a sin offering, like the first one. 16 And he presented the burnt offering and offered it according to the rule. 17 And he presented the grain offering, took a handful of it, and burned it on the altar, besides the burnt offering of the morning. 18 Then he killed the ox and the ram, the sacrifice of peace offerings for the people. And Aaron’s sons handed him the blood, and he threw it against the sides of the altar. 19 But the fat pieces of the ox and of the ram, the fat tail and that which covers the entrails and the kidneys and the long lobe of the liver—20 they put the fat pieces on the breasts, and he burned the fat pieces on the altar, 21 but the breasts and the right thigh Aaron waved for a wave offering before the Lord, as Moses commanded.
-We see here that Aaron too can follow directions and we see the process carried out that God had given Moses and the Israelites.
22 Then Aaron lifted up his hands toward the people and blessed them, and he came down from offering the sin offering and the burnt offering and the peace offerings. 23 And Moses and Aaron went into the tent of meeting, and when they came out they blessed the people, and the glory of the Lord appeared to all the people. 24 And fire came out from before the Lord and consumed the burnt offering and the pieces of fat on the altar, and when all the people saw it, they shouted and fell on their faces.
-This is why everything had to be done perfectly or else, the Lord could not appear in the form of fire as God the Father does. If He had appeared and a single tiny detail had not been performed, it would not be perfect and would misrepresent who the Lord is. Since every step was taken exactly correct, as we read in these verses and can prove, the Lord was able to appear. This doesn’t mean that if we perform some kind of magic ritual or incantation we can make God or some spirit appear but rather it is the other way around. God has told the Israelites what to do so that He can appear to them. God is the one who set the terms for this ritual and there is a reason for every single tiny step and the order of every single action and item used.