When the people of Israel were in the desert, God provided manna for their daily sustenance. He gave them some basic instructions about collecting the manna, but some people didn’t listen – or at least they didn’t do what God said.
He warned them not to stockpile the manna and try to save some for the next day. Those who did, found their hoard had become smelly and infested. I think the lesson was to rely on God for their daily bread, in this case manna.
On the day before the Sabbath, God said to collect enough for two days, because the next day was a day of rest. Those who ignored his instruction found no manna on the Sabbath and presumably went hungry. The lesson was for them to rest as God commanded them to do.
God provided for the people, but only those who obeyed him completely realized his full provision.
I wonder how often God does the same with us, trying to provide what we need, only for us to miss out because we don’t do what he says.