Oneness of God:
He is One and the Only One. He is not two in one or three in one. This means that Islam rejects the idea of trinity or such a unity of God which implies more than one God in one. Firm belief in the oneness of God is the primary faith and conviction of the religion of Islam.
The Quran says: "If there were therein Gods beside Allah, then verily both (the havens and the earth) had been disordered. Glorified be Allah, the Lord of the Throne, from all that they ascribe (unto Him)."
The Quran says: " Say: He is Allah the One and Only; Allah the Eternal Absolute; He begetteth not nor is He begotten; And there is none like unto Him."