 A precedent of such evil tendency was dangerous, and it was imperatively necessary, therefore, as well for the priests themselves as well as for the sacred things, that God should give a punishment.Whether Nadab and Abihu neglected to follow God's outlined sacrificial system out of presumptuousness, or out of thoughtlessness and inattention, their fault was severely punished so that all might learn to comply exactly with God's commands, and not try to change them or explain them away.The mixing of falsehood with the word of God was a serious sin.