What did God create on the 7th day?

Answer 1

1 So the creation of the heavens and the earth and everything in them was completed. 2 On the seventh day God had finished his work of creation, so he rested from all his work. 3 And God blessed the seventh day and declared it holy, because it was the day when he rested from all his work of creation.

4 This is the account of the creation of the heavens and the earth.

... God created everything on the first 6 days, and rested on the 7th, so nothing.

Answer 2

Day by day, God created the universe and its contents (Genesis ch.1).God created the universe out of nothing (Exodus 20:11, Isaiah 40:28; Rashi commentary to Genesis 1:14; Maimonides' "Guide," 2:30).Note that the Torah, in describing the Creation, deliberately employs brevity and ellipsis, just as it does in many other topics. See the Talmud, Hagigah 11b.

• On day 1: God created the universe in general, light, and this Earth. The light was not the same as that of the sun. Rather, it was light that God created before the sun, and which emanated from a point in space without any physical source; like what we might term a "white hole."
  
• On day 2: God created the separation between the Earth and the upper atmosphere.
  
• On day 3: God separated the continents from the oceans, and created plants.
  
• On day 4: God created the sun, moon, and stars.
  
• On day 5: God created birds and fish.
  
• On day 6: God created animals and people.
  
• On day 7: God ceased creating, thereby creating the concept of rest.
  

See also:

Is there evidence against Evolution?

Can you show that God exists?

Seeing God's wisdom