Charles Ellicott Commentary Exodus 16:23

"And he said unto them, This is that which Jehovah hath spoken, Tomorrow is a solemn rest, a holy sabbath unto Jehovah: bake that which ye will bake, and boil that which ye will boil; and all that remaineth over lay up for you to be kept until the morning." — Exodus 16:23 (ASV)

Tomorrow is the rest of the holy sabbath to the Lord. —Hebrew, tomorrow is a rest of a holy Sabbath to Jehovah. If the translation of the Authorised Version were correct, the previous institution of the Sabbath, and the knowledge of it (if not its observance) by the Israelites would be necessarily implied, as the double use of the article would otherwise be unintelligible. But in the Hebrew there is no article either here or in Exodus 16:25. The absence of the article indicates that what is announced is a new thing—if not absolutely, then at least to those to whom the announcement is made.

Much, no doubt, may be said in favour of a primeval institution of the Sabbath (see the comment on Genesis 2:2-3); and its observance in a certain sense by the Babylonians (see the first Note on Exodus 16:5) is in favour of its having been known to the family of Abraham. But during the Egyptian oppression, continued observance would have been impossible, and the surprise of the elders, as well as the words of Moses, show that at this time the idea was, to the Israelites, practically a novelty.

Bake ... Seethe.—These directions imply a very different substance from any of the natural forms of manna. The heavenly "gift" could be either made into a paste and baked, or converted into a porridge.