John Calvin on Numbers 26:60-62

60. And unto Aaron was born Nadab. Since two of Aaron’s four sons were cut off by a sudden death, the dignity of the high-priesthood, which depended on the life of two persons, appeared to be endangered. And with this view Moses repeats the history already given, in order that God’s wonderful providence might be more clearly perceived in the preservation of this order, with which the safety of the whole Church was connected. Unquestionably, unless other families had been much more prolific, the whole tribe of Levi would have consisted of very few persons; yet, if we come to compare them, their fecundity will be incredible, inasmuch as 23,000 are numbered, whereas the sacerdotal race issued from only two heads. But God exalts His Church to pre-eminence by ways and means unknown to men, in order that His power may be magnified in this weakness. Moreover, the cause of their death is again recorded, that the priests, being admonished by this warning, may not only more diligently beware of wilful sacrilege, but also of error and negligence.