This is what the LORD has commanded: 'Gather of it, each one of you, as much as he can eat. You shall each take an omer, according to the number of the persons that each of you has in his tent.'" And the people of Israel did so. They gathered, some more, some less. But when they measured it with an omer, whoever gathered much had nothing left over, and whoever gathered little had no lack. Each of them gathered as much as he could eat. And Moses said to them, "Let no one leave any of it over till the morning." But they did not listen to Moses. Some left part of it till the morning, and it bred worms and stank. And Moses was angry with them. Morning by morning they gathered it, each as much as he could eat; but when the sun grew hot, it melted.
Exodus 16:16-21
There were two stipulations with regard to the gathering of the manna. One was that the people were to gather enough for one day only at a time, and nothing was to be left over until the next day; the other was that on the sixth day they were to gather two days' supply, for there would be none to gather on the Sabbath. There are lessons here of deep significance. For one thing, God was intent on teaching His people to depend upon Him day by day, and to live one day at a time. One Jewish Rabbi says in this connection, in answer to the question why the Lord did not give the Israelites enough for a year at a time, 'I will answer with a parable. Once there was a king who had a son to whom he gave a yearly allowance on the same day each year. But it soon happened that the day on which the allowance was due was the only day of the year when the father saw his son; and so the king changed his plan and gave his son daily supplies and then the son visited his father every morning. Thus did God deal with Israel'. This orthodox Jewish interpretation is, of course, perfectly right. It was a lesson of daily dependence that God was intent on teaching His people. This very aptly illustrates the truth that the spiritual life is a present reality, not a future anxiety. The essence of salvation is that we are saved from the burdens of the past and the anxieties of the future in order that we might live fully in the present, trusting in the sufficiency of the divine provision. To have gathered two days' supply, as some did (20) was evidence of lack of trust, and this is what God was concerned to correct in His people (see Matthew 6:25ff, especially 32).