Charles Spurgeon 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 unto the LORD:

And yet the Sabbath had not been instituted according to law, which proves that its foundation lay deeper and earlier than the promulgation of the Ten Commandments; it is bound up with the essential arrangement of time since the creation: This is that which the Lord hath said, Tomorrow is the rest of the holy sabbath unto the Lord.

And he said to them, This is that which the LORD has said.

How often could that answer be made to us!

God hears our prayer, and we run and say, "What a wonderful thing! God has heard my prayer." This is that which the LORD has said. Is it a strange thing that what Jehovah has said is proved to be true, and is it a subject for surprise that he should keep his promise?

You dishonour God when you talk in this way.