"And on the seventh day God finished his work" (Gen. 2:2). The Holy One, blessed be He, created seven dedications, six of them He dedicated, and one is reserved for the (future) generations. He created the first day and finished all His work and dedicated it, as it is said, "And it was evening, and it was morning, one day" (Gen. 1:5). He created the second day and finished all His work and dedicated it, as it is said, || "And it was evening, and it was morning, a second day" (Gen. 1:8); and so through the six days of creation.
He created the seventh day, (but) not for work, because it is not said in connection therewith, "And it was evening and it was morning." Why? For it is reserved for the generations (to come), as it is said, "And there shall be one day which is known unto the Lord; not day, and not night" (Zech. 14:7).