John Calvin Commentary Exodus 19:3

"And Moses went up unto God, and Jehovah called unto him out of the mountain, saying, Thus shalt thou say to the house of Jacob, and tell the children of Israel:" — Exodus 19:3 (ASV)

And Moses went up. It is probable that Moses sought, as he was accustomed, retirement, in order to seek counsel from God. For he is not speaking of some new or unusual circumstance, but of a custom previously observed, because he did not dare to stop anywhere, nor make any further advances, except as far as was prescribed to him by the mouth of God. His going up to God simply means that he went out of the camp, so that far from the multitude and from all distractions, he might in secrecy and quiet inquire of God what His will was. For he did not, like the superstitious, choose a lofty position so that he might be nearer to God; but he withdrew from every disturbance so that he might engage all his senses in learning.

Afterwards, however, he adds that he had obtained more than he had hoped for, because God, beyond His usual custom, addressed him concerning the renewal of His covenant. And the opening words refer to this—“Thus shalt thou say to the house of Jacob, and tell the children of Israel;”—in which the repetition and diversity of expression are emphatic, as if He were speaking of a very serious matter and would thus awaken greater attention.