Unity of God as stated by The Old Testament:

From: http://religionandscience.info/Unity%20of%20God%20as%20stated%20by%20the%20Holy%20Bible3.html

1. Hear O Israel, the Lord our God is one Lord and you shall love the Lord with all your soul and with all your heart. (Deuteronomy 6:4)
2. To you it was shown, that you might know that the Lord is God, there is no other besides him. (Deuteronomy 4:35)
3. Know therefore this day, and lay it to your heart, that the Lord is God in heaven above and on the earth beneath, there is no other. (Deuteronomy 4:39)
4. And Ezra said, “Thou art the Lord ,thou alone, thou hast made heaven, the heaven of heavens, with all their host, the earth and all that is on it, the seas and all that is in them; and thou preservest all of them; and the host of heaven worship thee.”(Nehemiah 9:6)
5. those who chose another God multiply their sorrows;
Their libations of blood I will not pour out;
Or take their names upon my lips.
6. You are my witnesses, says the Lord, “and my servants whom I have chosen, that you may know and believe me and understood that I am He. Before me no god was formed, nor shall be any after me, I am the lord and besides me there is no savior. (Isaiah 43:10-11)
7. Thus says the Lord the King of Israel and his redeemer, the Lord of hosts, “I am the first and I am the last; besides me there is no God (Isaiah 44:6)
8. I am the Lord and there is no other, besides me there is no God. (Isaiah 45:5)
9. Declare and present your case; let them take counsel together! Who told this long ago? Who declare it was old? Was it not I, the Lord? And there is no other God besides me, a righteous God and a savior; there is no besides me. Turn to me and be saved, all the ends of the earth! For I am God and there is no other. (Isaiah 45:21-22)
10. Remember the former thing of old, for I am God and there is no other; I am God and there is none like me. (Isaiah 46:9)