John Calvin Commentary Numbers 20:6

"And Moses and Aaron went from the presence of the assembly unto the door of the tent of meeting, and fell upon their faces: and the glory of Jehovah appeared unto them." — Numbers 20:6 (ASV)

And Moses and Aaron went from the presence. It is probable that they fled in fear, since the tabernacle was a kind of refuge for them from the violence of the people.

Still, we may conjecture from other passages that they had consideration not only for themselves, but also for the wretched people, however unworthy they might be of it. Thus, when they threw themselves upon their faces, I understand that they did so, not so much (to pray) that God would protect them from the wrath of their enemies, but also that He would calm these madmen by some appropriate remedy.

Their agitation, however, appears to have been so great as to deprive them of their ordinary self-restraint. Nor, indeed, did God test their faith and patience, as He often had on other occasions; perhaps because He saw that they were too overwhelmed to be able to persevere inflexibly in pious zeal, patience, and care for the public good. Consequently, the appearance of God’s glory to them was a support for their weakness, in a case of extreme need.

This example shows us how earnestly God should be entreated constantly to support us with new supplies of His grace, since otherwise the boldest of us all would fail at every moment. The invincible resolution of Moses had so often overcome every obstacle, that there seemed to be no fear of his being in danger of falling; yet the conqueror in so many struggles at length stumbles in a single act. Therefore, we should more carefully bear in mind the exhortation of Paul: Because

it is God which worketh in us both to will and to do of his good pleasure, we should work out our own salvation with fear and trembling (Philippians 2:12, 13).