It does not say. Genesis 1:26 has God say "Let us make humans in our image" and never explains the "us." A study Bible, the New Oxford Annotated Bible, says it probably means God's heavenly court, the beings around God's throne in 1 Kings 22:19 and Job 1:6. Older Christian writers read it as the Trinity, Father, Son and Holy Spirit.
The same plural shows up again in Genesis: "like one of us" in Genesis 3:22 and "let us go down" in Genesis 11:7. Michael Coogan and Cynthia Chapman's Old Testament textbook reads all three the same way: probably the divine council, which it calls the assembly of the gods. The textbook says this council is called in for the last and most important act of creation.
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