These being the first offerings that ever were offered by the levitical priesthood, according to the newly-enacted law of sacrifices, the manner of offering them is particularly related, that it might appear how exactly they agreed with the institution.
1. Aaron with his own hands slew the offering (Leviticus 9:8), and did the work of the inferior priests; for, great as he was, he must not think any service below him which he could do for the honour of God: and, as Moses had shown him how to do this work decently and dexterously, so he showed his sons, that they might do likewise; for this is the best way of teaching, and thus parents should instruct their children by example.
Therefore as Moses before, so Aaron now offered some of each of the several sorts of sacrifices that were appointed, whose rites differed, that they might be thoroughly furnished for every good work.
2. He offered these besides the burnt-sacrifice of the morning, which was every day offered first, Leviticus 9:17. Note, Our accustomed devotions morning and evening, alone and in our families, must not be omitted upon any pretence whatsoever, no, not when extraordinary services are to be performed; whatever is added, these must not be diminished.
3. It is not clear whether, when it is said that he burnt such and such parts of the sacrifices upon the altar (Leviticus 9:10-20), the meaning is that he burnt them immediately with ordinary fire, as formerly, or that he laid them upon the altar ready to be burnt with the fire from heaven which they expected (Leviticus 9:24), or whether, as bishop Patrick thinks, he burnt the offerings for himself with ordinary fire, but when they were burnt out he laid the people's sacrifices upon the altar, which were kindled and consumed by the fire of the Lord.
I would rather conjecture, because it is said of all these sacrifices that he burnt them (except the burnt-offering for the people, of which it is said that he offered it according to the manner, Leviticus 9:16, which seems to be equivalent), that he did not kindle the fire to burn them, but that then the fire from the Lord fastened upon them, put out the fire that he had kindled (as we know a greater fire puts out a less), and suddenly consumed the remainder, which the fire he had kindled would have consumed slowly.
4. When Aaron had done all that on his part was to be done about the sacrifices he lifted up his hand towards the people, and blessed them, Leviticus 9:22. This was one part of the priest's work, in which he was a type of Christ, who came into the world to bless us, and when he was parted from his disciples, at his ascension, lifted up his hands and blessed them, and in them his whole church, of which they were the elders and representatives, as the great high priest of our profession.
Aaron lifted up his hands in blessing them, to intimate whence he desired and expected the blessing to come, even from heaven, which is God's throne. Aaron could but crave a blessing, it is God's prerogative to command it.
Aaron, when he had blessed, came down; Christ, when he blessed, went up.