John Calvin Commentary Numbers 20:25

"Take Aaron and Eleazar his son, and bring them up unto mount Hor;" — Numbers 20:25 (ASV)

Take Aaron and Eleazar his son. Aaron’s successor was to be designated while he himself was still living. This was, first of all, so that the perpetuity of the priesthood might be secured, and secondly, to prevent the people, with their usual rashness, from taking upon themselves the election in a matter depending solely on the will of God.

For, unless Eleazar had been appointed priest while his father was still alive, the office itself might fall into disrepute, since the high dignity of any individual is often resented. Therefore, so that their perverse envy would not drive them to repudiate the priesthood, God anticipates them and provides that religion, which ought to be perpetual, should not perish along with the men.

Again, we know how great the audacity of this people was in innovation. Therefore, to prevent them from appointing for themselves a priest from another tribe on their own whim, it was well that the one whom God approved should be firmly established, so that he would be received without controversy as the true and lawful one.

In this matter, an external symbol was used: Eleazar was invested with the sacred garments. This does not refer to the shirt or the slippers, but to the sacerdotal ornaments. The effect of this ceremony, therefore, was as if Aaron were resigning to his son the office which he had discharged until that day.

Moreover, it is worthy of observation that Aaron voluntarily yielded not only his dignity but also his life. His faith was confirmed by this proof, for if he had not been persuaded that an inheritance was laid up for him in heaven, he would not have so calmly departed from the world.

Since, however, he composed himself to die just as if he were merely lying down on his bed, it is altogether beyond doubt that his mind was lifted up to the hope of a blessed resurrection, from which arises a cheerful readiness to die.

And it is probable that his faith was elevated and strengthened when he saw that the testimony of God’s grace, on which the safety of the people depended, was made to rest upon the person of his son. For it was exactly as if the image of the Mediator were set visibly before his eyes.

This consolation, then, being of no ordinary character, rendered him superior to the terrors of death. Meanwhile, Eleazar succeeded in the presence of the people, so that his authority might not in the future be exposed to their murmurs.