Why didn't God feed them on the 7th day the same way he had fed them the other 6 days of the week?
Because under the Law of Moses... Saturday sabbath was a thing.
Moses hadn't been given the law yet. The manna was given in Exodus 16, the water from the rock in Exodus 17, and the they got to Mt Sinai in Exodus 19. So the law of the Sabbath hadn't been written in stone but had come directly from the mouth of God.
Exo 16:1
And they took their journey from Elim, and all the congregation of the children of Israel came unto the wilderness of Sin, which
is between Elim and Sinai, on the fifteenth day of the second month after their departing out of the land of Egypt.
Exo 16:2
And the whole congregation of the children of Israel murmured against Moses and Aaron in the wilderness:
Exo 16:3
And the children of Israel said unto them, Would to God we had died by the hand of the LORD in the land of Egypt, when we sat by the flesh pots,
and when we did eat bread to the full; for ye have brought us forth into this wilderness, to kill this whole assembly with hunger.
Exo 16:4
Then said the LORD unto Moses, Behold, I will rain bread from heaven for you; and the people shall go out and gather a certain rate every day, that I may prove them, whether they will walk in my law, or no.
Exo 16:5
And it shall come to pass, that on the sixth day they shall prepare
that which they bring in; and it shall be twice as much as they gather daily
Exo 16:6
And Moses and Aaron said unto all the children of Israel, At even, then ye shall know that the LORD hath brought you out from the land of Egypt:
Exo 16:7
And in the morning, then ye shall see the glory of the LORD; for that he heareth your murmurings against the LORD: and what
are we, that ye murmur against us?
Exo 16:22
And it came to pass,
that on the sixth day they gathered twice as much bread, two omers for one
man: and all the rulers of the congregation came and told Moses.
Exo 16:23
And he said unto them, This
is that which the LORD hath said, To morrow
is the rest of the holy sabbath unto the LORD: bake
that which ye will bake
to day, and seethe that ye will seethe; and that which remaineth over lay up for you to be kept until the morning.
Exo 16:24
And they laid it up till the morning, as Moses bade: and it did not stink, neither was there any worm therein.
Exo 16:25
And Moses said, Eat that to day; for to day
is a sabbath unto the LORD: to day ye shall not find it in the field.
Exo 16:26
Six days ye shall gather it; but on the seventh day,
which is the sabbath, in it there shall be none.
Exo 16:27
And it came to pass,
that there went out
some of the people on the seventh day for to gather, and they found none.
Exo 16:28
And the LORD said unto Moses, How long refuse ye to keep my commandments and my laws?
Exo 16:29
See, for that the LORD hath given you the sabbath, therefore he giveth you on the sixth day the bread of two days; abide ye every man in his place, let no man go out of his place on the seventh day.
Exo 16:30
So the people rested on the seventh day.
I think the emphasis on the day misses the point of the bread God supplied them for the 7th day.
They laid it up till morning, and it did not stink, neither was their any worm therein.
The bread was without corruption.
What is the bread? Jesus is the bread, it is his word that is incorruptable.
And on the sixth day God prepared this particular bread with no corruption for the 7th day.
Jesus is the truth. God's word is truth. God's word is incorruptible. Like the manna given on the sixth day that would hold over through the 7th day. That's today.
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