The One God = the Father of Jesus:
The Concept Is Easy
The ground fallacy of the Trinitarian argument is that Jesus is to be identified as Yahweh. Since the Father is Yahweh, saying that Jesus is Yahweh makes two Yahwehs! Trinitarians are fond of saying "Jesus is Yahweh," but they seem to forget that they believe the Father is also Yahweh. Two who are Yahweh makes two Yahwehs.
Jesus however, in his classic statement of monotheism, said "you [Father] are the only one who is truly God" (John 17:3). In that phrase we have both the words monos (alone, only) and theos (God). Jesus excluded himself from the Godhead by saying that his Father is "the only one who is truly God." According to the laws of language which we all understand, this means that Jesus is not the only true God. Only the Father belongs to the category of "the only true God." Jesus is another person. He is the Son and he was sent by the Father who alone is the true God.
Jesus appears to think that this understanding is vital to the quest for eternal life: "This is eternal life: that they come to know YOU [Father], the only true God, and Jesus Christ whom you commissioned."
This really is not difficult, and it was not meant to be! J.A.T. Robinson at Cambridge stated the obvious when he wrote, "In the first place it should be noted that John is as undeviating a witness as any in the New Testament to the fundamental tenet of Judaism, of unitary monotheism (cp. Rom. 3:30; James 2:19). There is the one, true and only God (John 5:44; 17:3). Everything else is idols (1 John 5:21)."
The same scholar is right to point out that the NT sometimes uses the same language of God and of Jesus. That is true. Jesus is functioning for the Father and is His deputy. But Jesus is not the One God. Only His Father is actually the One God (John 17:3). With this truth in place, Jews and Muslims can join the Christian quest, based on the assurance that only one Person is the true God. Jesus is His unique prophet, servant and Messiah. Paul summed up this non-complicated idea with this: "There is one God and one mediator between the one God and man, the man Christ Jesus" (1 Tim. 2:5). With these statements all arguments can be safely laid to rest.
Jesus, quoting the most important of all commands, said, "The Lord our God is one Lord" (Mark 12:29). This is the Greek NT version of "Yahweh our God is one Yahweh" (Deut. 6:4-5). Yes, Jesus does things which Yahweh does, because his Father, Yahweh, has authorized this. Jesus and God work together in perfect harmony. Bur there is only one Lord God: "The Lord our God is one Lord" (not two or more Lords!)
distinction between the One God, the Father, and the Son is that the Son of God
is begotten. This word "begotten" means he has a beginning. But God
(Yahweh) has no beginning. He is self-existing:
"I am who I am" (Exod. 3:14). The Son of God not only had a beginning of existence, began to exist in time (Matt. 1:18, 20; Luke 1:35; 2 Sam. 7:14-16), but he also died and was tempted and fell asleep. But God does not do these things. God is not only unbegotten, i.e. He has no beginning, but He also cannot die. That should convince anyone that Jesus who died cannot be God! A person who is incapable of death cannot die! Is that so hard? The Son of God was limited in his knowledge, and said so (Mark 13:32).
If we identify Jesus as Yahweh we are committing ourselves to belief in two who are Yahweh and this is two Yahwehs â€” one too many. This would contradict Jesus who said "the Lord our God is one Lord." The Lord God of the Bible, who is always a WHO and never a WHAT, "is one Yahweh [LORD]." That is easy to understand. It also sounds like Jesus, who said exactly that: "You, Father, are the only one who is truly God" (John 17:3).
God has revealed Himself using human language in Scripture (thank God He has!). It is a cop-out to say that the Bible's human, yet inspired language is inadequate. It is all we have. God speaks in Scripture, and not once did He say that He is an "essence" or a "What." There are thousands of examples of the various words for God in the Bible (Adonai, Lord, YHVH, Elohim, God, and Theos). Not once is God called an essence (ousia in Greek). The word "God" never means a triune Being. James White, struggling to defend the Trinity, says that the word God "can refer to all three persons at once," but he offers no example.  There are none.
In desperation some have resorted to a very easily detected language muddle. They have alleged that the Hebrew word for "one" is really "compound one." The fact that no standard lexicon of the biblical Hebrew language ever heard of this idea does not deter them one moment. It may be difficult for them to look this up in a Hebrew lexicon. But they can ask anyone who knows Hebrew or look up all the occurrences of echad ("one" in Hebrew) and see for themselves. (The word for "one" in Hebrew appears in masculine and feminine forms.)
Some rely on someone else. A zealous reader ... who is determined to believe in the triune God writes to inform us that Jimmy Swaggart Ministries told him that "one" may mean "more than one," i.e. "compound one." It is hard to respond respectfully (as we should) to this sort of claim. Would Jimmy Swaggart claim to be any sort of expert in this field? I doubt it. He does not claim to define English words. He knows that Webster's does much better at that. The equivalent for biblical Hebrew is the Brown, Driver and Briggs Hebrew and English Lexicon of the Old Testament, or other equally good ones available on good Bible software. The facts of the language can be examined easily in English by looking up all the 970 appearances of the word "one" (echad) and seeing what they mean. It is a complete falsehood to state that echad means "more than one." "Abraham was one single person [echad]," Ezekiel wrote in 33:24. Moses said that God is "one single Lord." (Deut. 6:4 quoted by Jesus in Mark 12:29). That is not so hard.
"One" in English and in Hebrew means one and not two. Ponder that statement from Jesus: "The Lord our God is one Lord" (Mark 12:29). What are you hearing there? Three Lords? Or one Essence in three Persons? The language of Jesus is refreshingly straightforward and comforting. He often spoke of a child-like approach being the one he treasured most in his people.
"God is one Essence in three Persons" is completely foreign to the words of Jesus. The absence of the word "Trinity" in the Bible might not be a difficulty for Trinitarians, but the total absence of the concept of the Trinity should be cause for concern. "God" in Scripture never signifies God, the triune Essence. Does that not strike churchgoers as astonishing?
Here are some more helpful examples of that word "one" (echad): One place (Gen. 1:9), one man (Gen. 42:13), one law (Ex. 12:49), one side (Ex. 25:12), one ewe lamb (Lev. 14:10), one of his brethren (Lev. 25:48), one rod (Num. 17:3), one soul (Num. 31:28), one of those cities (Deut. 4:42), one way (Deut. 28:7), one ephah (1 Sam 1:24), one went out into the field (1 Kings 4:39). One shepherd (Ezek 37:24), one basket (Jer. 24:2), one thing (Ps. 27:4), two are better than one (Ecc. 4:9), for one day or for two (Ezra 10:13). Abraham was only one person (Ezek. 33:24), a unique day Zech 14:7. 
So we invite any reader to show from a standard lexicon of Hebrew that "one" means more than one. Now of course "one" can describe a compound noun. You can have "one family." But think carefully. What does the word "one" mean here? Your 12-year-old will be insulted by the question! "One family" means just that. Not two families or three families!
I am sure readers are finding their way into the subject by now. "The Lord our God is one Lord," says Mark 12:29, reporting Jesus' own precious words. Is that clear? "One Lord" does not mean three Lords or two Lords. Well did a very learned scholar bewail the fact that the Trinity is really a contradiction in terms: "It is a contradiction, indeed, and not merely a verbal contradiction, but an incompatibility in the human ideas conveyed. We can scarcely make a nearer approach to an exact enunciation of it [defining God], than of saying that one thing is two things." 
Tragically noble believers have had to die at the hands of cruel and misunderstanding church authorities determined to impose their confusing concept of God, based on Greek philosophical terminology, on them. The death penalty was issued for non-Trinitarians. At other times, believers in God as a single Person are just told that they are heretics who will burn forever! As a race how far have we progressed?
That God is a single (echad) Divine Person is said over and over again in the Bible. The repetition is massive and impressive. We all know that a pronoun stands for a noun, and single personal pronouns tell us that we are dealing with a single p/Person. God has chosen to reveal Himself not only as "one Lord," "one Father," but as "I" and "Me," and "He" and "Him." Those words do not confuse us. We use them all the time with no possibility of being misunderstood. So with God. He reveals Himself (note Himself, as a singular personal pronoun) thousands and thousands of times as one single Divine Person. There is no other way known to language by which one can define himself as a single Person.
But with our fatal tendency as humans to spoil a marvelous, unifying and health-giving truth, we appear to prefer torturing our brains with the impossible idea that God is both three and one at the same time. No Bible verse (out of 31,000!) has the word "three" next to God. The Bible writers and Jesus whose teaching is recorded for us had never heard of a triune God, except perhaps as a pagan concept to be rejected. Yes, of course the Father, Son and holy spirit are quite often mentioned together, but in such verses, we never read that the three make up the One God. (1 John 5:7 in the KJV is a forgery, as is now publicly known to all.)
We invite readers to examine all points of view. By all means read what others have to say. But don't necessarily accept a "favorite" ministry as the last word on Hebrew words. They may just be passing on what they have heard, but have not verified. ...
The God of Jesus is the God of Israel and of the Bible. Ask any Jew about his God and he will shrink from the notion that God is more than one supreme Lord. Are Jews and their rabbis and rabbi Jesus to be rejected as not understanding the word "one"? It is a fascinating issue to search out. And while you are at it, why not write to the MacArthur Study Bible editors and ask them why they (inadvertently) misreported what the Bible actually says in Psalm 110:1. Will anyone accept the challenge to ask them a question? On Mark 12:36, "The Lord said to my Lord," they say "The first word for Lord is Yahweh, which is God's covenant name. The second word for Lord is a different word which the Jews used as a title for God ... Jesus was proclaiming [by quoting this verse] the Messiah's deity."
That second word is positively and definitely not the word Jews used for God! Ask any Jew. He will tell you the second "lord" in Psalm 110:1 is the Hebrew word adoni ("adonee") and in every one (not two!) of its 195 occurrences means a lord who is not God, but a human or occasionally angelic superior. Note the contradiction. The Study Bible asserts what is not true. The second "lord" they say is the word for God. It is not. It is the word which never means the supreme One God. The lesson is that believers are supposed to be alert and on the watch, not just believing everything they read from "favorite" teachers.
Will anyone report back on what the Study Bible might say? But don't let them fob you off with a nonanswer about Hebrew vowel points. The vowel points are part of our received text and we have fortunately complete certainty that there is no corruption of the text quoted by Jesus (Ps. 110:1, cited in the gospels). The Hebrew word "adoni" means "my lord," not Lord God. It is never the title of Deity. The Greek version of the Old Testament and the New Testament inspired in Greek render the word "adoni" perfectly as "my lord."
I trust our
readers will now see that as they bow in prayer, the universe is constituted
like this: There is one God, the Father, and no one
else but Him, and there is one Lord
He is not God but the Son of God. And within five minutes you can find out what "Son of God" means for Jesus, and how he acquired that title. Luke 1:35 is the key: "For this reason he will be the Son of God." The reason: God became His father by biological miracle in Mary. That explains what Son of God means. The angel was clear and concise. But the church's traditions have overwhelmed and suppressed the precious words of Gabriel. Point this out to your friends.
... Jesus is the Son of God, the second Adam. Jesus was created, begotten in the womb of the Jew Mary. Luke 1:35 gives us the perfect explanation of what it means for Jesus to be the Son of God.
If you get involved in an instructive discussion about Yahweh and who He is, here is a possible way to approach the question. How many Yahwehs are there? Is there just one Yahweh, or if Jesus is Yahweh, does that make two, and if you add the Holy Spirit does that make three? So is the one Yahweh (Mark 12:29) really three Yahwehs? That sounds like 3Xs make 1X. Logicians call that logical nonsense. The word YHVH [i.e. YAHWEH] needs to be given a clear definition so that we worship God "in spirit and truth." Truth is life-giving and health-giving (1 Tim. 6:3). Confusion and conflict in the mind does no one any good. It fosters an insidious dishonesty. The important thing for Christians is to follow Jesus' teaching, to sound like him, to recite and believe his creed and his definition of God. Is that asking too much?
 The Forgotten Trinity, p. 71.
 I am indebted for this list to Lindsey Killian and Dr. Emily Palik in their The God of the Hebrew Bible and His Relationship to Jesus.
 A.H. Newman, Sadler's Gloria Patri, p. 39.