Leviticus 10:2 New International Version (NIV)

So fire came out from the presence of the Lord and consumed them, and they died before the Lord.

Aaron’s sons were careless about following the laws. Performing the sacrifices was an act of obedience, and doing them correctly showed respect for God. It can be easy for us to grow careless about obeying God. We can slide into living our way. If either way was good, God would not have commanded us to live his way. God has good reasons for his commands. You can place yourself in danger if you get careless and disobey.