Genesis 2:2-3

2 By the seventh day God finished the work that he had been doing, and he ceased on the seventh day all the work that he had been doing. 3 God blessed the seventh day and made it holy because on it he ceased all the work that he had been doing in creation.

On “the seventh day” God “ceased” (or rested; the Hebrew word is sabat) the work of creation He had been doing. He stopped not because of fatigue but because He was finished. The seventh day or Sabbath day became, in Jewish law, a day of fellowship with God by, among other things, ceasing or resting from one’s earthly work.

The Sabbath day is a kind of picture of the rest of God. The first part of Hebrews chapter four has an excellent discussion of the Sabbath-rest of God. It is not just God’s rest, it is also ours if we will put our faith in Him and the One He sent. “So then, there remains a Sabbath rest for the people of God, for whoever has entered God’s rest has also rested from his works as God did from his.” (Hebrews 4:9-10, ESV)