‘And it happened on the sixth day that they gathered twice as much food, two omers for each one. And all the rulers of the congregation came and told Moses.'
The gathering of twice as much was in accordance with the instruction in Exodus 16:5. It is noteworthy that Moses was keeping a close watch on what was happening, for the ‘rulers', the chiefs, reported back what was happening.
“The rulers of the congregation.” As with ‘children of Israel' which was abbreviated to ‘Israel' when applied genitivally to ‘the elders' (Exodus 3:16; Exodus 3:18), so ‘all the congregation of the children of Israel' can be abbreviated to ‘congregation' when used genitivally with ‘the rulers'. The ‘rulers' or ‘princes' are the leaders of the sub-tribes (Numbers 2:3 etc). The ‘congregation' means here the children of Israel as a whole.
The subject the rulers wanted to discuss was presumably as to what they should do about the extra that had been gathered. If they were fully familiar with the law of the Sabbath this is surprising as in that case they would have been expecting that food for the Sabbath had to be prepared the day before. (This is the first mention of the Sabbath in Scripture). Many therefore see this as suggesting that the Sabbath was not yet a recognised institution at this point in time. And this might be seen as backed up by Moses' explanation. Note that he speaks of ‘a sabbath' not ‘the Sabbath'.