Aaron’s sons offered “strange fire” and God put them to death because of it. They were instructed the proper protocols for offering the sacrifices but they chose to do it their own way instead.

Refer also to Strange Fire

• Exodus 30:9 :: Aaron is warned against offering “strange incense”
• Exodus 34:25
• Leviticus 1:7 :: Nadab and Abihu get the instructions
• Leviticus 10:2 :: Nadab and Abihu are consumed by God’s judgement fire
• Leviticus 19:5–8 :: when sacrificed food is eaten and not eaten
• Numbers 1:47–51 :: only Levites could handle tabernacle things
• Numbers 3:4 :: record of Nadab and Abihu dying childless
• Numbers 3:10 :: authorized persons put to death
• Numbers 3:38 :: authorized persons put to death
• Numbers 4:1–20 :: Kohathites, porters of holy things, weren’t allowed to see them covered by the Levites
• Numbers 8:23–26 :: God sets work lifespan for Levites
• Numbers 9:1–14 :: rules for observing Passover in edge cases
• Numbers 16:1–50 :: God judges Korah and those who rebelled against Moses
• Numbers 21:4–9 :: Snake on a pole
• Deuteronomy 12:1–14 :: Remove idolatrous things, follow God’s worship practices only
• Deuteronomy 12:29–31 :: don’t worship like the people you’re displacing
• Deuteronomy 16:1–8 :: passover festival rules
• Judges 17:1–13 :: God never said people could hire their own priest