John Calvin Commentary Exodus 19:23

"And Moses said unto Jehovah, The people cannot come up to mount Sinai: for thou didst charge us, saying, Set bounds about the mount, and sanctify it." — Exodus 19:23 (ASV)

And Moses said to the Lord. Because Moses was convinced that the people would be obedient, he replied that the decree already pronounced would be sufficient, and its repetition somewhat superfluous. For when he said that "the people cannot come up," he replied that he was putting himself forward in the name of all as their guarantor. He did this honestly and in accordance with the rule of charity; yet it appears from God’s reply that he was deceived, while judging others by his own feelings.

While, however, he unhesitatingly carried out the task allotted to him, it is clear that he preferred God’s command to his own preconceived opinion. He thus taught us by his example that whatever ideas may come into our minds, they must still be submitted to this yoke, so that God’s authority alone may have preeminence.

A question may arise because He mentions "the priests," since the priestly office had not yet been assigned to the Levites. Some, therefore, understand this to refer to all the first-born, because by ancient and common consent, it is accepted that they were always invested with the honor of the priesthood. However, although I readily admit that they were chosen from the first-born, I do not think it probable that out of such an immense multitude, there were special priests for every house.

Meanwhile, we may conjecture that since no pagan nations at that time were without priests, a similar system existed among the chosen people. For what common sense dictated to the blind, a purer religion surely showed more clearly: namely, that God’s worship should not be separated from the priesthood.