There's a rumor going around that the New Testament supposedly teaches a belief in three gods.
To begin with, it's important to understand that this false rumor does not exist by accident. It is based on deliberate brainwashing that has been promoted for 2,000 years, and its purpose is to present the New Testament as pagan. For example, see the false statement of Rabbi Daniel Ballas on the “hidabroot” website, where he claims that believers in Jesus believes there are three different gods: “According to their belief, the creator of the entire universe is nothing but three gods.”

But no, we absolutely do not believe in three gods!

God is ONE, as the Prophet Isaiah said: “Thus says the Lord, the King of Israel and his Redeemer, the LORD of hosts: “I am the first and I am the last; besides me there is no god.”
Now check this quote out:
“The mystery in the word YHWH: there are three steps, each existing by itself; nevertheless they are One, and are so united that one cannot be separated from the other. The same Holy and Ancient One, appears as three heads within one, and He is the head elevated three times. The Ancient Holy One, described as three and also the other lights, which are delegated from His source are included in the three.”
Sounds like a Christian quote?
Well, it's NOT….
This is a quote from the most prestigious book in rabbinical mysticism – straight out of the Jewish book of The Zohar.
But wait, there is more….
“Hear, O Israel: The LORD our God, the LORD is one.”
Did you notice that God's name appears three consecutive times? The Jewish Zohar explains that the expression “Hear, O Israel: The LORD our God, the LORD is one”, is actually three who are one: 
“Only through faith, in the vision of the Holy Spirit, the mystery of the audible voice is similar to this, for though it is one,  yet it consists of three elements: Fire, air and water.”
The truth is, that the Jewish book of The Zohar goes in great depth into the subject it calls “Haraz de Shlosha” – “The Mystery of the Three”, about the nature of One God with three dimensions\persons. The Zohar refers to God as to three heads, three spirits, three ways of appearance, three names, and three shades of interpretations that describe the divine nature.
It would be interesting to know if Rabbi Daniel Ballas intends to blame the Jewish book of The Zohar as being a “Pagan Christian” book?
We cannot, and probably should not place God in a lab in an attempt to understand exactly who or what He is. He said in the past: “I am who I am.” And through Isaiah, He said: “My thoughts are not your thoughts.”
If, as human beings, we were able to fully understand God with our human minds, then we probably would not fear Him. We cannot worship a god that our mind is able to fully contain. While we can never fully understand God, it is still possible to find many clues throughout the Hebrew Scriptures (OT) that testify to His character.
To begin with, God is not made of matter, He is abstract. Yet, he can manifest Himself in material forms, whether it's in the form of a pillar of cloud and a pillar of fire, or as the Angel of God, or in the form of the Messiah. The Hebrew Scriptures describe God as One who sits up above, and at the same time, in the Temple. At the same time, He fills the prophets with His Spirit; and all of this, while His Glory fills the entire universe. Can you see how complex God is in the forms  and places in which He manifests?

In Isaiah 48:16, God says:
“Draw near to me, hear this:
from the beginning I have not spoken in secret,
from the time it came to be I have been there;
And now the Lord God has sent me, and His Spirit.”
Is God saying that YHWH sent Him together with His Spirit?

Genesis 1:26: “Then God said, “Let us make man in our image, after our likeness.”
Does God speak of Himself in plural form?
We can go on and on, and spend long hours quoting more verses throughout the Hebrew Scriptures, the writings of the Jewish sages and of course from the New Testament, that indicate that One God manifests Himself in three different persons. But you already got the idea.
God, who loves the humanity which He created, appeared to us in different persons. One of the forms in which God showed Himself to us, is in the form of the Messiah. He took on flesh, and demonstrated His love for us by suffering with us and for us. He sacrificed His own life on the cross so He could take our sins upon Himself, not so we worship Him out of fear of legalistic religious compulsion, but because we are grateful for His love and for what He has done for us.