And when Moses heard it,.... What they said, their complaint against him, for setting up Aaron for an high priest, and against Aaron for taking this honour to himself:

he fell upon his face; through shame, as the Targum of Jonathan, blushing at their sin, in opposing the ordinance of God; and through fear of the divine displeasure, and of the wrath of God coming upon them for such wickedness; and in order to pray to God for them to make them sensible of their sin, and give them repentance for it, and pardon of it, and avert his judgments from them such a conduct called aloud for.

When Moses heard these words of the rebels, he fell upon his face, to complain of the matter to the Lord, as in Numbers 14:5. He then said to Korah and his company, "To-morrow Jehovah will show who is His and holy, and will let him come near to Him, and he whom He chooseth will draw near to Him." The meaning of לו אשׁר is evident from בּו יבחר אשׁר. He is Jehovah's, whom He chooses, so that He belongs to Him with his whole life. The reference is to the priestly rank, to which God had chosen Aaron and his sons out of the whole nation, and sanctified them by a special consecration (Exodus 28:1; Exodus 29:1; Leviticus 8:12, Leviticus 8:30), and by which they became the persons "standing near to Him" (Leviticus 10:3), and were qualified to appear before Him in the sanctuary, and present to Him the sacrifices of the nation.

And when Moses heard it, he fell upon his face:

16:4 On his face - Humbly begging that God would direct and vindicate him. Accordingly God answers his prayers, and strengthens him with new courage, and confidence of success.

4. when Moses heard it, he fell upon his face-This attitude of prostration indicated not only his humble and earnest desire that God would interpose to free him from the false and odious imputation, but also his strong sense of the daring sin involved in this proceeding. Whatever feelings may be entertained respecting Aaron, who had formerly headed a sedition himself [Nu 12:1], it is impossible not to sympathize with Moses in this difficult emergency. But he was a devout man, and the prudential course he adopted was probably the dictate of that heavenly wisdom with which, in answer to his prayers, he was endowed.

16:1-11 Pride and ambition occasion a great deal of mischief both in churches and states. The rebels quarrel with the settlement of the priesthood upon Aaron and his family. Small reason they had to boast of the people's purity, or of God's favour, as the people had been so often and so lately polluted with sin, and were now under the marks of God's displeasure. They unjustly charge Moses and Aaron with taking honour to themselves; whereas they were called of God to it. See here, 1. What spirit levellers are of; those who resist the powers God has set over them. 2. What usage they have been serviceable. Moses sought instruction from God. The heart of the wise studies to answer, and asks counsel of God. Moses shows their privileges as Levites, and convicts them of the sin of undervaluing these privileges. It will help to keep us from envying those above us, duly to consider how many there are below us.