Genesis 2:3

And God blessed the seventh day, and sanctified it: because that in it he had rested from all his work which God created and made.

1. God blessed the seventh day and sanctified it, making it holy.
2. Although God is capable of long periods of work, He also enjoys and/or needs a rest from work.
3. The tradition of resting from work one day each week dates back to the creation of the world.
4. More masculine pronouns are used here in reference to God, reinforcing the idea that God is a male.
5. God apparently did not rest on the eighth day but resumed His work, whatever that was. Either that or the author of Genesis neglected to mention it or did not have that information.