"Hear O Israel, The Lord our God is one Lord" Deuteronomy 6:4
The key to having a proper relationship with God is to know his identity. Moses expressed to the children of Israel that the God whom they serve is one God in number. Meaning he is a singular God.
This revelation of the identity of God is the very foundation of the Jewish faith, and is called the "Shema" which is recited even until this day. It is traditionally known that Moses is the author of the first five books of the bible, the Torah. Moses as well as all of his Jewish counterparts who have labored in writing the books that make up the Old Testament were highly monotheistic believers. This is a key concept in understanding who God is; we must understand that he is one Lord.
The prophet Isaiah declared...
"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
The book of Isaiah holds some of the strongest declarations that the God of the Bible is one God. The Lord used the prophet Isaiah to emphatically proclaim his absolute oneness to such an extent, that he could not make this concept any simpler. The cries of Isaiah serve as a memorial for us today that beside God there is no other, he formed the earth all by himself.
There is one thing that God does not know, and that is another God.
“And Jesus answered him, the first of all the commandments is, Hear, O Israel; The Lord our God is one Lord: And thou shalt love the Lord thy God with all thy heart, and with all thy soul, and with all thy mind, and with all thy strength: this is the first commandment”. Mark 12:29-30
Jesus made it plain, quoting Deuteronomy 6:4 he lets us know that loving the one true God of the bible is the greatest commandment. Jesus Christ was completing his earthly ministry in telling the scribes this because he was in fact pointing the world unto himself, for the very God who gave Moses this commandment was resident in his body.
“To wit, that God was in Christ, reconciling the world unto himself...” 2 Cor 5:19
“And without controversy great is the mystery of godliness: God was manifest in the flesh, justified in the Spirit, seen of angels, preached unto the Gentiles, believed on in the world, received up into glory”. 1 Tim 3:16
Lets us understand, with all wisdom what the word of God declares concerning the identity of God. For the mighty God of the Old Testament prophets was manifest in the flesh and bruised for our iniquities to redeem us unto himself, and not another.
Min. John W. Jenkins