Charles Ellicott Commentary Leviticus 10:1

"And Nadab and Abihu, the sons of Aaron, took each of them his censer, and put fire therein, and laid incense thereon, and offered strange fire before Jehovah, which he had not commanded them." — Leviticus 10:1 (ASV)

And Nadab and Abihu. — Immediately after the divine manifestation of God’s acceptance of the services connected with the institution of the priesthood, and while the congregation were still expressing their profound thankfulness and joy, the assembled people saw a most daring act of sacrilege committed by two of the five newly-installed priests. They then had to witness the most awful punishment that befell the offenders.

The offenders were the two eldest sons of Aaron, who had received the high distinction of being invited to accompany their father and Moses to the summit of the hallowed mount (Exodus 24:1). The lesson for the Israelites was that the priests, though mediators between God and the people, are beset with the same infirmities as the laity and must not presume upon their office.

Each of them took his censer. — The sin of Nadab and Abihu was of a complicated nature, and involved and consisted of several transgressions:

1. They each took his own censer, and not the sacred utensil of the sanctuary.
2. They both offered it together, whereas the incense was only to be offered by one.
3. They presumptuously encroached upon the functions of the high priest; for according to the Law, the high priest alone burned incense in a censer. (Numbers 17:11). The ordinary priests only burned it on the golden altar in the holy place (Exodus 30:7–8), or on the bronze altar as a part of the memorial (See Leviticus 2:2-3, Leviticus 2:16, and so on). The case of Korah and his company was an exception, since it was ordered by Moses for a special purpose (Numbers 16:6–25).
4. They offered the incense at an unauthorized time, since it was apart from the morning and evening sacrifice.

And offered strange fire. — They filled their vessels with common fire instead of taking it from the holy fire of the altar, which was always to be used in burning incense (Leviticus 16:12). It is with reference to this practice that we are told, And the angel took the censer and filled it with fire off the altar (Revelation 8:5). Ancient tradition says that Nadab and Abihu had partaken too freely of the drink offering and performed their service in a state of intoxication, when they were incapable of distinguishing between what was legal and illegal.

So general was this tradition that it is actually embodied in the Palestinian Chaldee Version of Leviticus 10:9, which contains the solemn warning against wine for those engaged in the service of the sanctuary, and which is regarded as a sequel to this awful catastrophe. Others, however, suppose that the phrase “strange fire” denotes fire that was not offered according to the prescribed law, just as “strange incense” is used to mean incense not prepared in the manner ordered by the Law (Exodus 30:9).

Before the Lord. — This may mean before the door of the sanctuary , or in front of the Holy of Holies . As the dead bodies are said in Leviticus 10:4 to have lain in the court of the tabernacle, the former must be the meaning in this passage.

Which he commanded them not. — According to a figure of speech frequently used in Hebrew, where the negative form is used for the emphatic affirmative, this phrase is better rendered, “which he had strongly forbidden them.” Though the command is only expressed in Leviticus 16:12, there can hardly be any doubt that it was previously given by Moses, since it is implied in Leviticus 1:7; Leviticus 6:12. We find a similar reference to a well-known statement, though not recorded here, in the following verse.