The Burning Of The Sons Of Aaron

Filii autem Aaron, qui, imponentes altari ignem alienum, igne divino exusti sunt, illos significaverunt qui, Dei traditione contempta, alienas doctrinas appetunt, et magisteria humanae institutionis inducent. Quos increpat Dominus et objurgat in Evangelio, dicens: 'Rejecistis mandatum Dei, ut traditionem vestram statuatis.' Videtur et ignem alienum incendere, quisquis, corporeae vel saecularis alicujus cupiditatis ignem in sacrario sui cordis accendens, audet altaribus Domini appropinquare. Quae non recipiunt, nisi illius ignis accensionem de quo ait Dominus: Ignem veni mittere in terram. Hoc igne nos Dominus Jesus semper incendat, ut illuminemur in sensibus, ne flagremus in vitiis. Sanctus Isidorus Hispalensis,Mysticorum Expositiones Sacramentorum Seu Quaestiones In Vetus Testamentum, In Leviticum, Caput VIII Source: Migne PL 83.325

The sons of Aaron, they who placed unhallowed fire on the altar and with Divine fire were burnt up, 1 signify those who are contemptuous of the traditions of God and grasp after strange teachings, and introduce instructions of human provenance. The Lord cries out against these and rebukes them in the Gospel, saying, 'You reject the command of God that you might set up your own tradition.' 2 It seems that to burn with unhallowed fire refers to anyone who has the fire of bodily or worldly desire burning in the sanctuary of his heart and who dares approach the altar of the Lord. They are not received unless they are inflamed with the fire of which the Lord says, 'I have come to place fire on the earth.' 3 With this fire the Lord Jesus always inflames us, that we be illuminated in our senses, lest we be burnt up in our vices. Saint Isidore of Seville, Expositions of Sacred Mysteries or Questions on the Old Testament, On Leviticus, Chap 8  1 Lev 10.1-3 2 Mt 15.3 3 Lk 12.49