Let’s address your question by reaching back and reading Genesis 1:26-27, “And God said, Let us make man IN OUR IMAGE, after our likeness: and let them have dominion over the fish of the sea, and over the fowl of the air, and over the cattle, and over all the earth, and over every creeping thing that creepeth upon the earth. So God created man IN HIS OWN IMAGE, in the image of God created he him; male and female created he them.”  Notice how the Lord determines to create man “in OUR image” and then we read that He did, indeed, create man “in HIS own image.”  In these two verses, we get the truth of the ONENESS of who God is and we also get a great hint about how that God exists in a state that is more than one.  We often say that God is one yet exists in three persons.

With that in mind, let’s go back and read the first verse in the Bible, Genesis 1:1, “In the beginning God created the heaven and the earth.”  The word ‘God’ comes from the Hebrew word ‘elohiym’ which references God in a plural form.  ‘Elohiym’ is a plural word denoting a singular god.  That word is used 31 times in the first chapter alone.  It is in the New Testament that we get the full truth that God, although one, exists in the form of the Father, the Son, and the Holy Spirit.  I suppose one of the greatest examples of this truth is found at the occasion of the baptism of the Lord Jesus.  We read in Luke 3:21-22, “Now when all the people were baptized, it came to pass, that Jesus also being baptized, and praying, the heaven was opened, And the Holy Ghost descended in a bodily shape like a dove upon him, and a voice came from heaven, which said, Thou art my beloved Son; in thee I am well pleased.”  At the Lord’s baptism, we learn that the Holy Ghost, in the form of a dove, descended upon Him.  We hear the voice of the Father declaring from the opened Heaven, “Thou are my beloved Son; in thee I am well pleased.”  Here in this one place, we witness the Father, the Son, and the Holy Ghost…yet there is only one god as we read in Isaiah 45:5, “I am the LORD, and there is none else…” 

Now let’s read Genesis 3:22, “And the LORD God said, Behold, the man is become as one of us, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever.”  Here, God is called “the LORD God”, which in the Hebrew is “Jehovah Elohiym.”  “Jehovah”means the self-existent or eternal One.  Jehovah Elohiym is the creator, yet He was not created.  He has ALWAYS EXISTED.  He has existed by His own will and power.  Again, in this verse, He uses the word ‘us’.  Who is He speaking to?  He is quite naturally speaking to the whole of His being…the Father, Son, and Holy Ghost. 

Some have supposed that in the above verse, God is speaking to His angels, telling them that man had now become as He and His angels were, having the ability to discern between good and evil, as a result of when Adam and Eve ate of the tree of the knowledge of good and evil.  However, referring again to Genesis 1:26 when the Lord said, “Let US make man in our image,” I believe it is only natural that He is continuing to speak to the complete Godhead in this situation.  (421.4)