From the Doctrine of New Jerusalem Concerning the Lord, number 45, we learn that God is One. 

45.  From the numerous passages quoted from the Word in the preceding chapter, it is evident that the Lord is called Jehovah, the God of Israel and of Jacob, the Holy One of Israel, Lord, and God, and also King, the Anointed, and David, from which it may be seen, as yet however as through a glass, darkly, that the Lord is God Himself, from and about whom is the Word. Now it is known in the whole world that God is one, and no man possessed of sound reason denies it. It remains therefore to confirm this from the Word and, in addition, that the Lord is that God. 

i. That God is one, is confirmed by these passages of the Word:

Jesus said, The first of all the commandments is, Hear, O Israel, The Lord our God is one Lord; therefore thou shalt love the Lord thy God with all thy heart, and with all thy soul (Mark 12:29, 30). 

Hear, O Israel, Jehovah our God is one Jehovah; and thou shalt love Jehovah thy God with all thy heart, and with all thy soul (Deuteronomy 6:4, 5). 

One came unto Jesus and said, Good Master, what good thing shall I do that I may have eternal life? Jesus said unto him, Why callest thou Me good? There is none good but the one God (Matthew 19:16, 17). 

That all the kingdoms of the earth may know that Thou alone art Jehovah (Isaiah 37: 20). 

I am Jehovah and there is none else there is no God besides Me that they may know from the rising of the sun, and from the west, that there is no God besides Me: I am Jehovah and there is none else (Isaiah 45:5, 6). 

O Jehovah of Armies, God of Israel, that dwellest on the cherubim, Thou art the God, even Thou alone, over all the kingdoms of the earth (Isaiah 37:16). 

Is there a God besides Me? and a Rock? I know not any (Isaiah 44:8). Who is God save Jehovah? and who is a Rock save our God? (Palms 18:31). 

ii. That the Lord is that God, is confirmed by these passages of the Word:
Surely God is in thee, and there is none else, there is no God. Verily Thou art a God that hidest Thyself, O God of Israel, the Savior (Isaiah 45:14, 15). 

Have not I Jehovah? and there is no God else besides Me, a just God and a Savior, there is none besides Me. Look unto Me that ye may be saved, all the ends of the earth; for I am God, and there is none else (Isaiah 45:21, 22). 

I am Jehovah, and besides Me there is no Savior (Isaiah 43:11). I am Jehovah thy God, and thou shalt acknowledge no God but Me; for there is no Savior besides Me (Hosea 13:4). 

Thus saith Jehovah the King of Israel, and his Redeemer Jehovah of Armies, I am the First and I am the Last, and besides Me there is no God (Isaiah. 44:6). 

Jehovah of Armies is His name, and thy Redeemer the Holy One of Israel the God of the whole earth shall He be called (Isaiah. 54:5). 

In that day Jehovah shall be king over all the earth; in that day there shall be one Jehovah, and His name one (Zechariah 14:9). 

As the Lord alone is the Savior and the Redeemer, and as it is said that Jehovah is that Savior and Redeemer, and that there is none besides Him, it follows that the one God is no other than the Lord. 

To read more on this topic go to Son of God-Son of Man and Trinity Explained.