God blessed the seventh day (i.e., Sabbath) for both physical and spiritual reasons. It is to be a special day of rest and a memorial, or occasion of reflexion and praise to Him, for the completion of His created work.
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God did not rest on the seventh day of creation for His own sake (as if He were tired), but as an example for us to follow. Rest is necessary for our spiritual, physical, mental, and emotional well-being. Our creator provided the Sabbath as a special blessing for His people, to renew and refresh them on a regular basis.
He designed it as a day of rest, worship and fellowship with Him. The Sabbath principle is so important that God made it one of the Ten Commandments for those who would become His covenant people.
Thanks for reading and stay blessed.