The First Commandment was given to Moses ~3300 years ago at Mt Sinai by people from Thiaoouba (יהוה in Hebrew). Moses wrote this commandment down in Hebrew, along with the other nine, in the second of his books, called Exodus, clearly referencing Thiaoouba (יהוה) as a source.
The five books of Moses are the basis of the so-called Old Testament. For this reason, the First Commandment is the foundation of both Judaism and Christianity.
Careful studies of original texts reveal, that the First Commandment (Exodus 20:3) originally recorded by Moses in Hebrew is mistranslated and hence misinterpreted in all languages on Earth.
Traditional translation (for example Aryeh Kaplan ) is as follows:
(20:3) "Do not have any gods before Me. Do not represent (such gods) by any carved statue or picture or anything in the heaven above or the earth below or in the water below the land. Do not bow down to or worship them."
My translation is this: (20:3) Do not have any gods before Me. Do not represent (me) by any carved statue or picture or anything in the heaven above or the earth below or in the water below the land. Do not bow down to or worship them.
In traditional (Kaplan) translation, the second sentence (such gods) contradicts the intention of the first. If all other gods are forbidden to begin with, WHY devote the next two sentences to them? Also, the singular (statue or picture) in the second sentence contradicts plural "gods" in the first. This indicates, that the second sentence refers to the singular object mentioned in the first sentence. The ONLY singular object there that qualifies is God itself.
My translation is explicitly re-confirmed later in (20:20): "Do not make a representation of anything that is with Me". Such an explicit and precise repeat re-confirms the importance of this advice. Note, that no other commandment is re-confirmed that way.
Honestly translated First Commandment, reinforced by (20:20), explicitly and specifically forbids people creating any religion, any altar, any church and any clergy whatsoever, simply because all of these things fundamentally mis-represent God, who does NOT need a proxy of any kind. Could this fundamental conflict with clergy be a reason why Moses was eliminated and his body never found?
Many christian priests try to cover up their explicit abuse of the First Commandment by claiming that Jesus "replaced" it. They should study Jesus' own words recorded in their own bible: (Matthew 5:17) "DO NOT SUPPOSE that I come to abolish the Law and the prophets. I did not come to abolish, but to complete."
Abuse of the First Commandment (misrepresentation of God) is a source of untold human misery for thousands of years. All conflicts, brainwash, wars, are based on doctrines that ruthlessly contradict the First Commandment. We have eyes, but do we see?
 The Living Torah, translated by Aryeh Kaplan, Maznaim Publishing Corporation, NY, Jerusalem 1981
 The New English Bible, New Testament, Oxford University Press, Cambridge University Press 1961