God has many commandments. But the FIRST (and therefore the most important) of all His commandments is that there is only ONE God.
The word ONE as applied to God means His absolute oneness. Meaning that He is God alone; there is no other God with Him or beside Him. God identified Himself as the Holy One and not as the Holy Trinity. The following verses support this view:
1. And Jesus answered him, The first of all the commandments is, Hear, O Israel; The Lord our God is one Lord: (Mark 12:29; cf. Deuteronomy 6:4)
2. "... there is one God; and there is none other but he." (Mark 12:32)
3. " ... there is none other God but one." (1Corinthians 8:4)
4. Remember the former things of old: for I am God, and there is none else; I am God, and there is none like me. (Isaiah 46:9)
5. "I am the LORD, and there is none else, there is no God beside me..." (Isaiah 45:5)
6. Thus saith the LORD the King of Israel, and his redeemer the LORD of hosts; I am the first, and I am the last; and beside me there is no God. (Isaiah 44:6)
7. "See now that I, even I, am he, and there is no god with me ..." (Deuteronomy 32:39)
8. For thou art great, and doest wondrous things: thou art God alone. (Psalms 86:10)
9. "I am the LORD, your Holy One ..." (Isaiah 43:15)
10. To whom then will ye liken me, or shall I be equal? saith the Holy One. (Isaiah 40:25)
11. That all the people of the earth may know that the LORD is God, and that there is none else. (1Kings 8:60)
12. Know therefore this day, and consider it in thine heart, that the LORD he is God in heaven above, and upon the earth beneath: there is none else. (Deuteronomy 4:39)
If a person believes and worships in more than one God, other than the "Holy One", he is breaking the FIRST of all the commandments of God and is committing the FIRST & GREAT sin, for breaking God's commandments is sin (1John 3:4).
