The Trinity. Next question.
Discussion
If you think the Trinity isn't in the Bible, you haven't read the Bible.
It was not originally from the Holy Bible.
See how your reasoning is superficial?
It has support but is not explicitly in Holy Scripture. Oneness Pentecostals reject the Trinity because they can't find it in their bibles.
Jesus didn't write the New Testament. His followers did, and *all of* His teachings were believed before they were written.
And that is just one more of the reasons why no one should meddle with the Holy Scriptures. Even less so heretics who consciously opted for changing sentences and ripping books out on a whim.
Once you read "History of the heresies and their refutations", from Saint Alphonse-Marie de Ligório, you will see how well documented is the whole process of the protestant stupidity and arrogance.