When Moses still lived in the house of Pharaoh, he saw the labor of the children of Israel. The book of Jasher tells us that he went to Pharaoh and requested that the Israelites be given one day off out of seven every week.
Jasher 70:41-48 “And the day arrived when Moses went to Goshen to see his brethren, that he saw the children of Israel in their burdens and hard labor, and Moses was grieved on their account. And Moses returned to Egypt and came to the house of Pharaoh, and came before the king, and Moses bowed down before the king. And Moses said unto Pharaoh, I pray thee my lord, I have come to seek a small request from thee, turn not away my face empty; and Pharaoh said unto him, Speak. And Moses said unto Pharaoh, Let there be given unto thy servants the children of Israel who are in Goshen, one day to rest therein from their labor. And the king answered Moses and said, Behold I have lifted up thy face in this thing to grant thy request. And Pharaoh ordered a proclamation to be issued throughout Egypt and Goshen, saying, To you, all the children of Israel, thus says the king, for six days you shall do your work and labor, but on the seventh day you shall rest, and shall not preform any work, thus shall you do all the days, as the king and Moses the son of Bathia have commanded. And Moses rejoiced at this thing which the king had granted to him, and all the children of Israel did as Moses ordered them.”
Then when Moses returned to Egypt to lead Israel out of Egypt we find this statement from Pharaoh.
Exodus 5:5 “And Pharaoh said, Behold, the people of the land now are many, and ye make them rest from their burdens.”
So it seems obvious that after Moses had fled Egypt that Pharaoh ignored the law and made Israel work seven days again. When Moses returned he got the Sabbath reinstated. Since it was law, Pharaoh could not stop it. The following verse means what it says in the Greek.
“There remaineth therefore a Sabbath to the people of God.” Hosea 4:9.