Then Nadab and Abihu, the sons of Aaron, each took his censer and put fire in it, put incense on it, and offered profane fire before the LORD, which He had not commanded them. So fire went out from the LORD and devoured them, and they died before the LORD. Then Moses said to Aaron, "This is what the LORD spoke, saying: 'By those who come near Me I must be regarded as holy; and before all the people I must be glorified'" (emphasis added).
Carefully note that the nature of the sin committed by Nadab and Abihu was that they offered profane fire before the Lord "which He had not commanded them."God did not say they offered profane fire "which was forbidden them."The fact that He had not commanded the use of the strange fire meant it was forbidden (God's silence in the matter meant an express prohibition of all profane fire). According to Leviticus 16:12 it would appear that the coals for the incense offering were to come from the fire on the altar of burnt offering. The priest then brought the coals from the altar of burnt offering into the Tabernacle, and on the altar of incense he spread the coals out mixing the coals and the incense which then filled the Holy Place. Apparently in a rather spontaneous act of worship (with perhaps "good intentions" cf. Lev. 9:22-24) they took fire from another source to praise God. God had just consumed the burnt offering by a miraculous display of fire, and all the people were in an enthusiastic state of shouting and falling on their faces before the Most High God. Leviticus 10:1 immediately follows with "Then." It may be that in all of the excitement, Nadab and Abihu, quite overcome by the demonstration of God's awesome power took fire from the quickest and nearest source available to them and immediately went into the Tabernacle to offer incense to the Lord God. They took liberties in worship which God had not given them, and they were slain. They added to the worship of God an act that was not specifically authorized by God. They brought their own man-made worship into the house of God, and His anger burned against them.
C. Objection
"But God has obviously relaxed His standards for He does not slay people on the spot for taking liberties in worship today. Why be so nit-picky today? We are under grace not law." I would have you remember that neither does God make a habit of immediately slaying those who lie to Him today though He did so to Ananias and Sapphira in Acts 5. Yet would anyone care to argue that lying to God is not as heinous to God today as it was to Him in Acts 5? Paul teaches, "Do you despise the riches of His goodness, forbearance, and long-suffering, not knowing that the goodness of God leads you to repentance" (Rom. 2:4). God's kind patience in forbearing with sin is not to be misunderstood as an approval of sin. It is God's objective Word and not my subjective feelings that assure me of God's approval of my worship.
_______ Presbyterian and Reformed Worship: Old and New by Kevin Reed A Review and Commentary upon Worship in Spirit and Truth, a book by John Frame. Reed shows how Frame has abandoned the Reformation, both scripturally and confessionally, in regard to worship.He also gives an excellent summary of historic Reformed views and then contrasts them with the novel ideas now being touted by Frame.
"All things considered, certainly it is no small condemnation of us to behold what an ardent zeal the holy martyrs had in the past, especially in comparison with the nonchalance we demonstrate. For as soon as a poor man of that time got so much as a little taste of the true knowledge of God, he did not hesitate to expose himself to the danger involved in confessing his faith. He would have preferred to be burned alive than to go so far as to commit some outward act of idolatry." - John Calvin
John Calvin on the Regulative Principle of Worship
"... which I commanded them not, neither came it into my heart."
"... God here cuts off from men every occasion for making evasions, since he condemns by this one phrase, "I have not commanded them," whatever the Jews devised. There is then no other argument needed to condemn superstitions, than that they are not commanded by God: for when men allow themselves to worship God according to their own fancies, and attend not to his commands, they pervert true religion. And if this principle was adopted by the Papists, all those fictitious modes of worship, in which they absurdly exercise themselves, would fall to the ground. It is indeed a horrible thing for the Papists to seek to discharge their duties towards God by performing their own superstitions. There is an immense number of them, as it is well known, and as it manifestly appears. Were they to admit this principle, that we cannot rightly worship God except by obeying his word, they would be delivered from their deep abyss of error. The Prophet's words then are very important, when he says, that God had commanded no such thing, and that it never came to his mind; as though he had said, that men assume too much wisdom, when they devise what he never required, nay, what he never knew."
"But such is the corrupt nature of man, that there is scarce any thing whereabout men have been more apt to contend with God from the foundation of the world. That their will and wisdom may have a share (some at least) in the ordering of his worship, is that which of all things they seem to desire. Wherefore, to obviate their pride and folly, to his asserting of his own prerogative in this matter, he subjoins severe interdictions against all or any man's interposing therein, so as to take away any thing by him commanded, or to add any thing to what is by him appointed. This also the testimonies recited fully express. The prohibition is plain, "Thou shalt not add to what I have commanded.'" - John Owen, Concerning Liturgies and Their Imposition (emphases added).