Exodus 16:19

And Moses said unto them
At the same time he gave the direction to them about gathering it, and measuring out to every man an omer:

let no man leave of it until the morning;
not that every man was bound to eat up the quantity distributed to him; he might give what he could not eat to those that could eat more, if there were any such; or he might give it to his cattle, or cast it away, but he was not to reserve it until the next day for his use; which was to teach him that God would bestow this benefit and blessing on him daily, and he might expect it, whose mercies are new every morning; and to instruct him to live every day upon the providence of God for his daily food; as indeed every man ought to do so, let his circumstances be ever so affluent; and, in a more spiritual and evangelic sense, it teaches believers to live continually every day by faith on Christ, and to say day by day, Lord, evermore give us this bread, ( John 6:34 ) .