There are several verses in the Old Testament where God speaks as a plurality. Many trinitarians quote these verses to help support theTrinitydoctrine because they strongly suggest that there is more than one person in the godhead.
"Then God said, “Let Us make man in Our image, according to Our likeness; and let them rule over the fish of the sea and over the birds of the sky and over the cattle and over all the earth, and over every creeping thing that creeps on the earth,” (Gen. 1:26, NASB).
"Then the Lord God said, “Behold, the man has become like one of Us, knowing good and evil; and now, lest he stretch out his hand, and take also from the tree of life, and eat, and live forever," (Gen. 3:22, NASB).
“Come, let Us go down and there confuse their language, that they may not understand one another’s speech,” (Gen. 11:7, NASB).
"Then I heard the voice of the Lord, saying, “Whom shall I send, and who will go for Us?” Then I said, “Here am I. Send me!” (Isaiah 6:8, NASB)
Those opposed to the doctrine of theTrinitysay that God is speaking of Himself in a "royal" sense, in a "plural of majesty." They can say this, but biblically there is never any account of a king or a ruler speaking of himself in a plural sense or in the third person. So, there is no biblical support for God using it of Himself in this way.
In regards toGen. 1:26, those who deny the Trinity say that when God says, "Let Us make..." He is speaking with theangelsin mind. The problem with this is that angels do not create. There is absolutely no biblical evidence that angels created anything at all. We see inIsaiah 44:24, "Thus says the Lord, your Redeemer, and the one who formed you from the womb, 'I, the Lord, am the maker of all things, Stretching out the heavens by Myself, And spreading out the earth all alone.'" God made all things alone. Therefore, the "us" in "Let Us make man in our image" cannot be the angels. Furthermore, people are not created in the image of angels, but of God.
The three verses in Genesis do not prove that the Trinity is true. However, they cannot be dismissed by the assumption that God is speaking of himself in a type of third person way.
Furthermore, notice in the fourth verse above,Isaiah 6:8, that God is speaking in the singular and then switches to the plural. He says, "Whom shall I send, and who will go for Us?" This on the unusual construction: the singular speaker refers to himself in the plural.