Nadab and Abihu were the two eldest sons of Aaron and they had the great privilege of climbing the mount of Sinai one day to see the God of Israel (Exodus 24:9-11). Afterwards they were given a great responsibility: to serve the LORD as priests for a perpetual statute (Exodus 28:1, 29:9). It was to be expected of them that, having seen the majesty of God, they would serve Him faithfully with fear, trembling and holiness. The Israelite priestly ministry was of high responsibility, and it was important that the priests rigorously fulfilled the determinations given by God, sometimes the death penalty being mentioned for infringements.
All the details of the tabernacle and of priestly service were specified in their minute detail by God to Moses. Among them was included the altar of incense in front of the veil before the ark of the covenant, on which Aaron was to burn fragrant incense every morning and evening. The LORD even dictated the recipe to make the fragrant incense prepared exclusively for this purpose (Exodus 30:7-10, 34-38). Common incense, or frankincense, (not the fragrant incense) was used for the grain offerings burnt to the LORD on the external altar (Levítico 2:1,2,15).
Once the tabernacle and its utensils had been made, they were consecrated together with Aaron and his sons, carefully obeying the instructions received. There were seven days of propitiation for the altar, at the end of which it became most holy, together with everything touching it. At the end of the ceremonial, fire came out from the LORD and consumed the holocaust and the portions of fat on the altar, signifying His approval to all that had been done, to the great joy of the people.
It was then that Nadab and Abihu "each took his censer and put fire in it, put incense on it, and offered strange 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." (Leviticus 10:1,2). In two other texts we read only that "Nadab and Abihu died when they offered strange fire before the LORD". (Numbers 3:4 e 26:61).
There is no general agreement on what this strange fire (or strange coals of fire) consisted of, in spite of many opinions and discussions which have been raised on the subject. The ones most heard are:
Perhaps they hadn't burned the incense with the burning coals of fire from off the altar, resulting from the fire which had come from before the LORD. This was only ordained later by the LORD (Leviticus 16:12) and they sinned by using other coals of fire in anticipation.
Perhaps they wanted to do what the high priest did twice a day, at a different time from what the LORD had designated.
Perhaps to come before the LORD they went beyond the veil, into the Holy of Holies, and so incurred the death sentence which would come later on (Levítico 16:1-2).
There is no doubt that their sin was disdain and disobedience, for they did that which He had not commanded them, and died when they came before the LORD. The LORD had said to Moses "By those who come near Me I must be regarded as holy; and before all the people I must be glorified." (Leviticus 10:3). The LORD had given instructions as to how, when and where they were to serve Him. Knowingly and deliberately they disobeyed Him. God is a jealous and holy God and so requires His servants to serve Him in His way. Obedience is better than sacrifice (Hebrews 10:5-10).
Nadab and Abihu disrespected God with their gesture. Each act in the ritual which God had so carefully determined in minute detail had a special meaning, a lesson to the people concerning holiness of the things of God, the seriousness of sin, and the price of its redemption, types which point to Christ. There was no place for the improvisation they made.
God's authority is emphasised in this incident, at the beginning of the covenant of the Law, just as it would later on with the death of Ananias and Sapphira at the beginning of the time of the Church (Acts 5:1-11). In both cases, death was the penalty for those who defied the authority of God, "For our God is a consuming fire" (Hebrews 12:29).
The high position of these men didn't make them immune to punishment, and the quickness of it was fulminating. The fire came suddenly from the LORD to kill them (like a bolt of lightning for it didn't consume their bodies or their clothes). Punishment for disobedience is given even today, and "For this reason many are weak and sick among you, and many sleep." (1 Corinthians 11:30), though not always as swiftly as in the case of Nadab and Abihu, and Ananias and Sapphira. .
Following this event the LORD spoke to Aaron, possibly for the first time as chief priest. His order was that he and his sons must never drink wine or strong (alcoholic) drink when they came to the tabernacle, under penalty of death. This order was a statute forever throughout their generations.
Although the New Testament does not contain an absolute prohibition like this, revelry, drunkenness and the drunkards are severely condemned (Romans 13:13; 1 Corinthians 5:11, 6:9-10; Ephesians 5:18; 1 Thessalonians 5:7-8). The overseers of the church must not drink wine or other alcoholic beverages (1 Timothy 3:3). Timothy, for example, drank only water (1 Timothy 5:23).
The use of alcoholic drinks and other drugs represses the senses so as not to be able to distinguish between the holy and the unholy, moral values are distorted and end up in total collapse. It could well be that Nadab and Abihu were under the influence of alcohol, hence this prohibition following immediately after the event. Instead of these substances, every believer should be filled with the Holy Spirit in order to better study the Word of God, transmit it to others, to be strengthened and guided in life (Ephesians 5:18).
Moses discovered soon after another transgression by the priests, in which the surviving two sons of Aaron participated: they hadn't eaten the sin offering in the holy place. It was a misunderstanding, explained by Aaron: because of the death of his two sons, he and his remaining sons had regarded themselves as unworthy. Moses accepted the explanation and they weren't punished, for they hadn't disobeyed on purpose.
God is being merciful today, giving time for repentance and for all to come to the knowledge of the truth. If it were not so, many would be dying like Nadab and Abihu, because they are trying to come to the presence of God in an improper manner, in disobedience to His instruction. We must come to Him in accordance with the conditions which He established. It is not for us to write the rules. God is the Saviour and only He can determine how we must be saved. The Lord Jesus declared that no-one comes to the Father other than through Him (John 14:6).
Finally, the commentator Scofield suggests that there are two "strange" things in these texts: common incense and fire which does not proceed from the altar. Common incense speaks to us of simulated or formal worship. Fire which does not proceed from the altar corresponds to animation due only to excitement of the senses, and to the substitution of devotion to some other thing, like religious enterprises or sects for devotion to Christ (See 1 Corinthians 1:11-13; Colossians 2:8, 16-19).
"Therefore gird up the loins of your mind, be sober, and rest your hope fully upon the grace that is to be brought to you at the revelation of Jesus Christ; as obedient children, not conforming yourselves to the former lusts, as in your ignorance; but as He who called you is holy, you also be holy in all your conduct, because it is written, 'Be holy, for I am holy.'" 1 Peter 1:13-16 (NKJV)