John Calvin Commentary Numbers 11:26

"But there remained two men in the camp, the name of the one was Eldad, and the name of the other Medad: and the Spirit rested upon them; and they were of them that were written, but had not gone out unto the Tent; and they prophesied in the camp." — Numbers 11:26 (ASV)

But there remained two of the men in the camp. It is not certain why they had not appeared among the others. I do not doubt at all that they were called for by Moses. Nor would they have been endowed with the same grace of the Spirit as the others if, through idleness or contempt, they had not come at the appointed time.

We may, therefore, probably infer that they did not actually receive the invitation because they could not be found. This is likely why God excused their ignorance.

However, it must be observed that they were kept back by the secret counsel of God. This was so that His grace might be made known by this remarkable proof among the common people in general, as not all of them were eyewitnesses, for the majority had not assembled at the Tabernacle. Therefore, so that its fame might spread more widely and reach even the most humble, God chose that this new and extraordinary gift of His Spirit should be conspicuous in the midst of the camp. This was to prevent any of the dullest or most unperceptive among them from pretending to be ignorant of it.

In fact, it is plain that they were all stirred by the miracle, for the “young man” mentioned would not have run to carry the incredible news to Moses unless struck by the novelty of the situation.