John Calvin Commentary Exodus 16:22

"And it came to pass, that on the sixth day they gathered twice as much bread, two omers for each one: and all the rulers of the congregation came and told Moses." — Exodus 16:22 (ASV)

And it came to pass on the sixth day. The violation of the Sabbath is not yet narrated, but only the stupidity or dense ignorance of their rulers is shown. For although they had heard from the mouth of Moses that God would on that day give what would be sufficient for two days’ provision, they still are amazed and report it to Moses as if it were something strange and unbelievable.

It is clear enough that they obeyed the command and did not spare their labor in gathering the double quantity, but their unbelief and folly reveal themselves in their astonishment when they see that God has really performed what he promised. We may surmise that they accurately observed what caused them so much astonishment, so that it follows that they refused to believe God’s word until its truth was effectively proven.

It came to pass, then, in God’s admirable wisdom, that their wicked and perverse doubting served both for the confirmation of the miracle and the observation of the Sabbath. Therefore, an occasion was given to Moses to again instruct them on what they otherwise, perhaps, would have neglected, namely, that they should honor the seventh day by a holy rest.