Although the Bible does not say Trinity or Trinitarian in it, it is in fact a real word. You can find it listed in the Websters Dictionary and Wikipedia. That's as far as I had gotten when searching. But for me that was enough proof.
Hank Hanegraff has a great book out. "The Complete Bible Answer Book. Collectors Edition." Now granted there are many that do not like him very well, but he answers so many questions and this book is so helpful. I am not going to write word for word what he has written on this subject, but enough to make a point.
First of all, in the Bible in Genesis 1:26 the first example of where the idea "trinity" came from.
"God said, 'Let us make man in our image, after our likeness." Notice the use of us and our. This implies that God is making a reference to others. Now we all know there is only one God.
Then he goes on to talk about the three planks to this. One being that it is stated that there is only one God. The second that there are many passages that mention the Father, Son, and Holy Spirit. He also stated:"The word "Trinity"--like "incarnation"--is not found in Scripture; however, it
aptly codifies what God has condescended t reveal to us about this nature and
being. In short, the Trinitarian platform contains three planks (1) there is but
one God; (2) the Father is God, the Son is God, and the Holy Spirit is God; (3)
Father, Son, and Holy Spirit are eternally distinct." (Hanegraff, H. 1984)
"The apostle Paul says that, 'there is but one God the Father'
(1 Corinthians 8:6). The Father, speaking of the Son, says, 'Your throne, O God,
will last forever" (Hebrews 1:8). And when Ananias 'lied to the Holy Spirit,'
Peter points out that he had 'not lied to men but to God (Acts 5:3-4)." (Hanegraff, H. 1984)
"The Father and Son love one another, speak to each other, (John 17:1-26), and
together send the Holy Spirit (John 15:26). Additionally, Jesus proclaims that
he and the Father are two distinct witnesses and two distinct judges (John
8:14-18). If Jesus were himself the Father, his argument would have been not
only irrelevant but also fatally flawed; and if such were the case, he could not
have been fully God." Hanegraff, H. 1984)
"It is important to note that when Trinitarians speak of one God they are
referring to the nature or essence of God. Moreover, when they speak of persons
they are referring to personal self-distinctions within the God head. Put
another way, we believe in one What and three Who's." (Hanegraff, H. 1984)
All throughout the Bible, it does talk about God as one as a central part. But
it also that God is "eternally three distinct persons," those being the Father,
Son, and Holy Spirit. (This paragraph and the next are not part of the quotes, but will not go back to regular left margin alignment. This is one problem I have with this program. If anyone knows how to fix it, please share for further posts. Thanks)
If you look at the Concordance under God, Jesus, and Holy Spirit. There are many scriptures that speak of them--not necessarily all three at one time--but of them being as one.
"James R. White, The Forgotten Trinity (Minneapolis: Bethany House, 2001), and
Robert Letham, The Holy Trinity: In Scripture, History, Theology, and Worship
(Phillipsburg, New Jersey; P&R Publishing, 2004)." (Hanegraff, H. 1984)