Will a person be held accountable for the whisperings of the word "God" to himself, and is uttering it aloud to oneself considered polytheism, and will sincere repentance be accepted if he repents?

Anyone who repents from any sin, no matter how great, must know that Allah accepts their repentance, for the Prophet, peace and blessings be upon him, said: "The one who repents from sin is like one who has no sin." As for the one afflicted by whisperings (waswas), they must disregard these whisperings and strive against their self, saying "I believe in Allah" whenever such thoughts occur to them. They should also know that they are not held accountable for what overwhelms them of these whisperings, for Allah does not burden a soul beyond its capacity. Their struggle to disregard these whisperings is hoped to be rewarded.