Abihu in Fausset's Bible Dictionary

Second son of Aaron by Elisheba (Exodus 6:23; Numbers 3:2). With Aaron, Nadab, and the 70 elders, he accompanied Moses up Sinai to a limited distance (Exodus 24:1). On his death by fire from heaven, in punishment for offering strange fire, (See AARON above. A standing example of that divine wrath which shall consume all who offer God devotion kindled at any other save the one Altar and Offering of Calvary, whereby "He hath perfected forever them that are sanctified."

Link: https://bible-history.com/faussets/A/Abihu/