Charles Ellicott Commentary Exodus 16:25

"And Moses said, Eat that to-day; for to-day is a sabbath unto Jehovah: to-day ye shall not find it in the field." — Exodus 16:25 (ASV)

Today is a sabbath—that is to say, a rest. By these words the Sabbath was either instituted, or re-instituted, and became henceforth binding on the Israelites.

Its essential character of a weekly “rest” was at once assigned to it:

1. by its name;
2. by God’s resting on it from His self-imposed task of giving the manna; and
3. by the rest which the absence of manna on the seventh day imposed on the people.

Thus the way was prepared for the stringent law of Sabbath observance laid down in the fourth commandment.