Trinitarians assert that the following verse teaches the Trinity:
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. (Genesis 1:26)
Trinitarians claim that the fact that the words of US, and OUR are mentioned proves a plurality of persons, hence proving the Trinity.
To make things more interesting let us read the passage that follows after it:
So God created man in his own image, in the image of God created he him; male and female created he them. (Genesis 1:26)
In the above passage we see that man is created in the image of God, or as it says, God created man in HIS image. If there was indeed a plurality of persons why didn't the passage state that God created man in their image, why use the singular HIS instead? This in itself is enough to shatter the Trinitarian argument of a plural persons.
The fact that words such as US and OUR are used by God is due to the plural of majesty, this also fits the context and language of the verses, verses 26-27, because as verse 27 says, God made man in HIS image, obviously it does not fit or go along to have God talking in plural persons then going back to singularity, but it does make sense when God is using a plural majesty, however so if he is a plural of persons then why go back and forth from supposed plural persons to a single person?
So to make everything simple, if this passage taught a Trinity then it would have said the following:
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 that creepeth upon the earth. So God created man in their own image, in the image of God created they him, male and female created they them (Genesis -27)
Also if we want to be more Trinitarian, then we must translate the word God into Gods, since Trinitarians believe the world Elohim is a literal plurality, hence it should be Gods.