Why does God refer to Himself in the plural in Genesis 1:26 and 3:22?

Genesis 1:26 says, “Then God said, 'Let us make man in our image, in our likeness, and let them rule over the fish of the sea and the birds of the air, over the livestock, over all the earth, and over all the creatures that move along the ground.'” Genesis 3:22 states, "And the LORD God said, 'The man has now become like one of us...'" There are other Scriptures in the Old Testament that refer to God using the plural. It is also interesting to note that "Elohim," one of the primary titles of God in the Old Testament (occurring over 2500 times), is in the plural.

Some people have used these scriptures to hypothesize that there is more than one God. We can rule out polytheism (belief in multiple gods), because that would contradict countless other Scriptures that tell us that God is one and that there is only one God. Three times in Isaiah 45 alone, He states: “I am the LORD, and there is no other; there is no God besides Me” (vv. 5,6,18). A second possible explanation is that God was referring to the angels by saying "us" and "our." However, the Bible nowhere states that angels have the same "image" or "likeness" as God (see Genesis 1:26). That description is given to humanity alone.

Since the Bible, and the New Testament especially, presents God as a Trinity (three Persons but only one God), Genesis 1:26 and 3:22 can only represent a conversation within the Trinity. God the Father is having a "conversation" with God the Son and/or God the Holy Spirit. The Old Testament hints at the plurality of God, and the New Testament clarifies this plurality with the doctrine of the Trinity. Obviously, there is no way we can fully understand how this works – but God has given us enough information to know that He does exist in three Persons, - Father, Son and Holy Spirit.