It is right to say God is one but there is more to it than that. For this reason it is written in Petach Eliyahu the words of the prophet Elijah “Opens Elijah the prophet to reveal God is one but not just one.” One is a limitation and God is unlimited. Elijah reveals a secret truth for the sake of World Unity and Peace which was hidden until today.
Religion simplifies faith into belief in one God and no other. The God of the Jewish people the God of Abraham, Isaac and Jacob is one God the Jewish God. The Jewish God is also called the King of the Universe. From there can be confused to think that the Jewish God and the Jewish people rule over the universe. This would put a limitation on God who is unlimited. The Jewish faith, the Jewish people conquered the land of Israel and established in the land of Israel the kingship of God of the Jewish faith.