‘In every religion’
In the Bhagavad Gita, Shri Krishna as the embodiment of transcendental reality states, “I am in every religion as the thread through the string of pearls, whenever you see extraordinary holiness and power raising and purifying humanity, know that I am there.” This ideal of a universal God has taught us to respect all divine incarnations as they are the manifestations of the same ultimate reality.
In the Gita, Shri Krishna further states: “Spiritually ignorant people do not see the immutable and transcendent reality behind God in human form.” Thus, they fail to see holiness in other divine incarnations and nurture feelings of animosity against followers of other religions.
Swami Vivekananda has stated: “When we recognize this truth of the universality of God, we will see the point of union with all other religions. Then there will be no place for persecution or intolerance. Instead, the whole force of all religions will be centered in aiding humanity to realize its own true divine nature.”
God is not a thing
Rushdy El-Ghussein, former president of the Islamic Society of Greater Kansas City: In Islam, there is only one God. God is Eternal and Absolute. He begets not and nor is he begotten, and there is nothing in creation like him.
God is the Creator, the Self-Sufficient, the Protector, the Aware. In the Qur’an, God has described himself with these and many more majestic, compassionate and powerful attributes. He is beyond definition, but evidence of his presence is everywhere: in our own bodies and capabilities, in our environment filled with resources and life, in the air and seas through which we travel and in the skies where we can see other suns and planets years away.
This is the God of Islam: a being so far beyond us, yet closer to us than our jugular vein, responding to us and calling us to listen to him
Therefore, it would be impossible for a Muslim to accept that a person who worships a man, animal or some other created thing (a statue, money, power, nature, etc.) is worshipping the one God.
That is not to say those of other faiths do not worship the one God. Jews and Christians are called in the Qur’an “the People of the Book” because they also received scriptures through their prophets. But all people must be careful not to mix the worship of other things with the worship of God. And God himself will sort out his own worshipers in the end.