The Sabbath, as outlined in
Genesis 2:1-3 and
Exodus 20:8-11, falls on the seventh day of the week, which is Saturday. However, it's important to note that according to
Genesis 1:5, God declared that a new day begins at sundown, not at midnight. Therefore, the Sabbath begins at sundown on Friday and ends at sundown on Saturday.
Here’s where the Sabbath was first instituted by God:
Thus the heavens and the earth were finished, and all the host of them. And on the seventh day God finished his work that he had done, and he rested on the seventh day from all his work that he had done.
So God blessed the seventh day and made it holy, because on it God rested from all his work that he had done in creation. (
Genesis 2:1-3 ESV)
Here God defines when a day commences and finishes, from evening to morning:
God called the light Day, and the darkness he called Night.
And there was evening and there was morning, the first day. (
Genesis 1:5 ESV)
Here’s the fourth commandment:
"
Remember the Sabbath day, to keep it holy. Six days you shall labor, and do all your work, but the seventh day is a Sabbath to the LORD your God. On it you shall not do any work, you, or your son, or your daughter, your male servant, or your female servant, or your livestock, or the sojourner who is within your gates. For in six days the LORD made heaven and earth, the sea, and all that is in them, and rested on the seventh day.
Therefore the LORD blessed the Sabbath day and made it holy. (
Exodus 20:8-11 ESV)