The obvious answer would seem to be at the giving of the ten commandments at Mt Sinai in Exodus chapter 20:
And God spoke all these words:
...
Remember the Sabbath day by keeping it holy. 9Six days you shall labor and do all your work, 10but the seventh day is a Sabbath to the LORD your God, on which you must not do any work—neither you, nor your son or daughter, nor your manservant or maidservant or livestock, nor the foreigner within your gates. 11For in six days the LORD made the heavens and the earth and the sea and all that is in them, but on the seventh day He rested. Therefore the LORD blessed the Sabbath day and set it apart as holy.
This is not the first time that the word comes in the Bible. In Gen 2 we read:
Thus the heavens and the earth were completed in all their vast array. 2And by the seventh day God had finished the work He had been doing; so on that day He rested from all His work.a
3Then God blessed the seventh day and sanctified it, because on that day He rested from all the work of creation that He had accomplished.
Just as in English there is a strong similarity between the Hebrew words for seventh and sabbath. But these verses seem to be an aside written by the author as a comment on the verse. It's not recording giving of the sabbath to Adam and Eve.
Before the giving of the ten commandments at Mt Sinai we have the account of the manna from heaven in Ex 16
Nevertheless, some of the people went out on the seventh day to gather it, but they found none. 28Then the Lord said to Moses, “How long will you c refuse to keep my commands and my instructions? 29Bear in mind that the Lord has given you the Sabbath; that is why on the sixth day he gives you bread for two days. Everyone is to stay where they are on the seventh day; no one is to go out.” 30So the people rested on the seventh day.
Now this happens before the Israelites get to Mt Sinai so when was the sabbath first given to the Israelites?
And God spoke all these words:
...
Remember the Sabbath day by keeping it holy. 9Six days you shall labor and do all your work, 10but the seventh day is a Sabbath to the LORD your God, on which you must not do any work—neither you, nor your son or daughter, nor your manservant or maidservant or livestock, nor the foreigner within your gates. 11For in six days the LORD made the heavens and the earth and the sea and all that is in them, but on the seventh day He rested. Therefore the LORD blessed the Sabbath day and set it apart as holy.
This is not the first time that the word comes in the Bible. In Gen 2 we read:
Thus the heavens and the earth were completed in all their vast array. 2And by the seventh day God had finished the work He had been doing; so on that day He rested from all His work.a
3Then God blessed the seventh day and sanctified it, because on that day He rested from all the work of creation that He had accomplished.
Just as in English there is a strong similarity between the Hebrew words for seventh and sabbath. But these verses seem to be an aside written by the author as a comment on the verse. It's not recording giving of the sabbath to Adam and Eve.
Before the giving of the ten commandments at Mt Sinai we have the account of the manna from heaven in Ex 16
Nevertheless, some of the people went out on the seventh day to gather it, but they found none. 28Then the Lord said to Moses, “How long will you c refuse to keep my commands and my instructions? 29Bear in mind that the Lord has given you the Sabbath; that is why on the sixth day he gives you bread for two days. Everyone is to stay where they are on the seventh day; no one is to go out.” 30So the people rested on the seventh day.
Now this happens before the Israelites get to Mt Sinai so when was the sabbath first given to the Israelites?