John Calvin Commentary Numbers 10:33

"And they set forward from the mount of Jehovah three days` journey; and the ark of the covenant of Jehovah went before them three days` journey, to seek out a resting-place for them." — Numbers 10:33 (ASV)

And they departed from the mount of the Lord. He calls Sinai “the mount of the Lord,” because in no other place had God’s glory been so conspicuously manifested. This, I admit, it had been called by anticipation (κατὰ πρόληψιν) before the promulgation of the law; but this name was imposed upon it afterwards to inspire eternal reverence for the law.

By “three days’ journey,” we must understand a continuous march of three days, for they did not pitch their tents until they reached the desert of Paran, but slept in the open air. When it is said that the ark went before them in the three days’ journey, there is no reference to its distance, as if it was sent forward three days ahead; but that it was so placed in their van that when the cloud settled upon it, they halted as at a station prescribed to them by God. This was the searching for a resting-place of which he speaks.