One God....

Originally posted by galveston75
Why was the comment made at Duet 6:4 that God was one God? What was the pourpose of this for that time?

That one's pretty easy. As has been stated, there were many folks around the Israelites who were polytheistic. Knowing how human nature works against the truth, God was warning His children from confusing what they knew about His essence (i.e., the triune nature of the Godhead) and equating Him with all of those other gods.

How do we know that they already held this understanding? See Genesis 1:26 for the first iteration of the same.