Deut. 6:4 "Hear. 0 Israel; Jehovah (singular) our God ('elohiym, Plural meaning god's), Jehovah is one ('echad meaning “united, one")
This scripture actually confirms the Trinity! If you will note, the word "God" is in the Plural!
1a) rulers, judges
1b) divine ones
2) (plural intensive - singular meaning)
2a) god, goddess
2b) godlike one
2c) works or special possessions of God
2d) the (true) God
Part of Speech: noun masculine plural
The word for "one" is also used to signify "united"!
H259 'echad ekh-awd'
A numeral from H258; properly united, that is, one; or (as an ordinal) first: - a, alike, alone, altogether, and, any (-thing), apiece, a certain [dai-] ly, each (one), + eleven, every, few, first, + highway, a man, once, one, only, other, some, together. (Strong's Concordance)
The same word 'echad is used in Genesis of the two, Adam and Eve, as being ONE FLESH!”
Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one ('echad) flesh.
The same word is used to define the plurality of the Godhead, as being united together as ONE, called Jehovah!
It may be interpreted like this. "Jehovah our Gods Jehovah is united, one".
This scripture is saying the Father, Son and the Holy Spirit, THEY are "Jehovah", and they are United. (I will cover more on Deut. 6:4 at the bottom of this page with more proof on this "unity of the trinity" verse)
The Plurality of the Godhead is clearly shown in the Old Testament scriptures as I show here!
Gen. 1:1 "In the beginning God ... ('elohiym - plural).."
Gen. 1:26 "Then God ('elohiym - plural) said `Let US make man in OUR image, according to Our likeness.”
(27) So God ('elohiym - plural) created man in HIS own image
We were NOT created in the image and likeness of angles! We were created in the likeness and image of GOD! So God could NOT be speaking to angles, or ANY other being in 1:26, other than the plurality of the Godhead, the Father, Son and Holy Spirit as we see the triune man whom God created in 1 Thes. 5:23
And the very God of peace sanctify you wholly; and I pray God your whole spirit and soul and body be preserved blameless unto the coming of our Lord Jesus Christ.
What is interesting, is how the triune man whom God created, was created in the Singular image of God “So God (Elohim-Plural, “god's”) created man in HIS own image (His-Sing.).
We see again, the singular and plurality when God speaks of the man whom he created, 1st in the singular, and then in the plural!
Genesis 1:27 So God created man in his own image, in the image of God created he him (Singular); male and female created he them (plural).
Then again, we see this plurality, become a singular! The TWO, are ONE!
Genesis 2:24 Therefore shall a man leave his father and his mother, and shall cleave unto his wife: and they shall be one ('echad) flesh.
Furthermore, you will see the plurality of the Godhead in the following verses!
And the LORD (Jehovah) God said, Behold, the man is become as ONE OF US, to know good and evil: and now, lest he put forth his hand, and take also of the tree of life, and eat, and live for ever: (KJV)
Go to, let US go down, and there confound their language, that they may not understand one another's speech.
Throughout the scriptures it does this, it speaks of them as one and then as separate.
God is NOT 3 God's, but rather ONE God "Jehovah" who is three persons
You will also note that the NWT shows Jehovah as a plurality in their own translation!
Gen. 18:1-2 Abraham sees Jehovah as three men (v. 3) Abraham speaks to Jehovah and says to Jehovah "YOU" and "YOUR" (The NWT identifies Plurality by using all capital letters as they did here where Abraham speaks to Jehovah in the plural).
(V. 5 and 9) When Jehovah speaks to Abraham Jehovah replies in the plural as though the plurality of God is speaking " THEY said...”
Although Jehovah was left standing before Abraham, you will note that in the 1984 edition of the NWT, that Lot identifies the other two men as "Jehovah"! “Then Lot said TO THEM; Not that, please, JEHOVAH!' (Gen 19:18) You must remember, Jehovah is still standing before Abraham when these two angels, whom Lot calls "Jehovah" go to Sodom (18:22). So Jehovah is shown here as 3 persons. One is standing before Abraham, while the other two persons, who are also Jehovah, go to get Lot out of Sodom!
While the plurality of the Godhead is clearly seen in the scriptures, the hearts and minds of these deceived souls have a veil of darkness that covers their ability to see Jesus and be saved!
2 Cor. 3:14-16 But their minds were blinded: for until this day remaineth the same vail untaken away in the reading of the old testament; which vail is done away in Christ.  But even unto this day, when Moses is read, the vail is upon their heart.  Nevertheless when it shall turn to the Lord (Jesus), the vail shall be taken away.
2 Cor. 4:2-6 But have renounced the hidden things of dishonesty, not walking in craftiness, nor handling the word of God deceitfully; but by manifestation of the truth commending ourselves to every man's conscience in the sight of God.  But if our gospel be hid, it is hid to them that are lost:  In whom the god of this world hath blinded the minds of them which believe not, lest the light of the glorious gospel of Christ, who is the image of God, should shine unto them.  For we preach not ourselves, but Christ Jesus the Lord; and ourselves your servants for Jesus' sake.  For God, who commanded the light to shine out of darkness, hath shined in our hearts, to give the light of the knowledge of the glory of God in the face of Jesus Christ.
The Father has commanded us to submit to the Son (1 Cor. 15:24-28 & Heb. 2:8) We are commanded to "Kiss the Son, lest He be angry” (Ps. 2:12) we are commanded to confess the name of the Son (Rom. 10:9; Phil. 2:9-11) we are commanded to bow our knees in worship to the name of Jesus (Phil. 2:10) and this GLORIFIES THE FATHER. (Phil. 2:11) Are you obeying God's command?
While the Watchtower denies the Trinity, making lots of noise about the word "Trinity" and it's absence in the scriptures, if you wish to be fair, the Watchtower has to confess that they are "Poly-theistic" (belief on more than one God). Not only is this doctrine not scriptural, but even more, the scriptures clearly deny such a belief! Fundamental Christianity declares that there is ONE God, who is 3 persons, as defined in Deut. 6:4.
When the "NWT" says that Jesus is "a god" in John 1:1 it has NOW invented 2 separate GOD's, therefore, they cannot claim to believe in ONE God as fundamental Christianity does, but rather two, independently, separate God's!. Since ONLY one of these God's can be the "True God" (John 17:3), the Watchtower is forced to admit that there is a "True God" who created a "False God" whom they must confess, is Jesus!
(see 22 Jesus" for more on Jesus)
For a more complete study, confronting the doctrine of the Oneness, or Jesus Only teachers, which is the flip side to the Jehovah's Witness heresy, go to Jesus Only
Returning to Deut. 6:4 Hear, O Israel: The Lord our God is one Lord:
In Dr. John Gill's Exposition of the entire Bible, we read:
The sense is, that he must first make a confession of his faith in God, which is contained in Deu_6:4 and then he must obey his commands; so that they plainly considered this, as the first and greatest of all. These words are frequent in the mouths of the modern Jews, in proof of the unity of God, and against a plurality in the Deity; but the ancient ones, not only consider them as a good and sufficient proof, that there is but one God, but as expressive of a Trinity in the Godhead: with a view to this text they observe (t), that
"Jehovah, "our God, Jehovah"; these are, "three degrees" (or persons) with respect to this sublime mystery, "in the beginning, God", or "Elohim, created", &c.''
And again (u),
"there is an unity which is called Jehovah the first, our God, Jehovah; behold! they are all one, and therefore called one: lo! these three names are as one; and although we call them one, and they are one; but by the revelation of the Holy Ghost it is made known, and they are by the sight of the eye to be known, that "these three are one", (see 1Jo_5:7, KJV) and this is the mystery of the voice that is heard; the voice is one; and there are three things, fire, and wind, and water, and they are all one, in the mystery of the voice, and they are not but one: so here, Jehovah, our God, Jehovah, these "three modes, forms", or "things", are one.''
Once more they (w) say,
"there are two, and one is joined to them, and they are three; and when they are three, they are one: these are the two names of hear, O Israel, which are Jehovah, Jehovah, and Elohenu, or our God, is joined unto them; and it is the seal of the ring of truth.''
To which I shall subjoin one passage more, where R. Eliezer is asking his father R. Simeon ben Jochai, why Jehovah is sometimes called Elohim, he replies (x), among other things;
"come see, there are "three degrees", (or persons,) and every degree is by itself; although they are all one, and bound together in one, and one is not separated from another.''
To believe this, is the first and chief commandment in the law, and is the principal article of the Christian faith; namely, to believe that there is one God, and that there are three persons, Father, Son, and Spirit, in the Godhead.
(t) Zohar in Gen. fol. 1. 3. (u) Zohar in Exod. fol. 18. 3, 4. (w) Ib. in Num. fol. 67. 3. (x) Zohar in Lev. fol. 27. 2.