First mention of a Sabbath is in Genesis, right?
Genesis 2:1-3 (KJV)
1 Thus the heavens and the earth were finished, and all the host of them.
2 And on the seventh day God ended his work which he had made; and he rested on the seventh day from all his work which he had made.
3 And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made.
But let us not assume anything, but look clearly at what the Scripture says.
First of all despite the fact that many Bibles have topic headings that say “Sabbath”, “First Sabbath”, or something similar, notice what word is missing from the text. Sabbath.
However, this verse is referenced several times later in Scripture as the basis for the Sabbath given to the Israelites.
Also the root word for “rest” is a similar word to the word Sabbath. “Shabath” meaning to celebrate, put away, cease, or rest. The word for the Sabbath is “shabbath” meaning intermission, translated as Sabbath in the KJV.
The first mention of the actual word “Sabbath” is in Exodus when the Lord is instructing the Israelites about the manna.
Exodus 16:23-29 (KJV)
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.
24 And they laid it up till the morning, as Moses bade: and it did not stink, neither was there any worm therein.
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.
26 Six days ye shall gather it; but on the seventh day, which is the sabbath, in it there shall be none.
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.
28 And the LORD said unto Moses, How long refuse ye to keep my commandments and my laws?
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.
Exodus 16:23 is literally “shabat shabaatown” – Sabbath the rest of.
This is the first Sabbath for the Israelite slaves. But they did not all obey. Some still went out to gather manna on the Sabbath but found none.