Lev 10:1 And Nadab and Abihu, the sons of Aaron, took either of them his censer, and put fire therein, and put incense thereon, and offered strange fire before the LORD, which he commanded them not.
Lev 10:2 And there went out fire from the LORD, and devoured them, and they died before the LORD.
Lev 10:3 Then Moses said unto Aaron, This is it that the LORD spake, saying, I will be sanctified in them that come nigh me, and before all the people I will be glorified. And Aaron held his peace.
You may ask why the LORD destroyed them by fire. Moses heard from God in verse 3, "I will be sanctified in them that come nigh". The sons of Aaron were not respecting the LORD, nor were their hearts holy before him. What did they do wrong?
1. They were not supposed to be in the holy of holies, this was Aaron's duty.
2. Their hearts were not prepared, they just entered into his presence without regard to his commands.
3. Two went in to the holy sanctuary, and the LORD commanded that only one enter.
4. They brought in strange fire, not fire from the altar that was fired by the LORD.
From this story I see that we who worship the LORD should worship him in spirit and in truth with holy hearts. We are not to enter into his presence with strange doctrines or with disrespect. I pastor teacher should prepare his heart to speak the message of God, not his own thoughts. To speak foolish words is as the son's of Aaron, being disrespectful and doing their own thing. The work of God is from the LORD, not from our imaginations. Our hearts can be wicked and we must prepare ourselves to do his Holy work. Aaron's sons rushed in without seeking direction from the LORD.
Zec 4:6 ... Not by might, nor by power, but by my spirit, saith the LORD of hosts.