Does a Muslim commit an act of disbelief by saying to himself, "I know the unseen"?

Allah Almighty does not hold a person accountable for the whispers of the self (waswas) and what revolves in their chest, as long as they do not speak or act upon it. This is based on the Prophet's (peace and blessings be upon him) saying: "Indeed, Allah has pardoned for my Ummah whatever whispers occur in their hearts, as long as they do not act upon it or speak about it." Waswasah is the recurring thought of something in the mind without the person feeling at ease with it or it settling in their mind. It is different from "hamm" (a strong intention) and "azm" (a firm resolve), for which one is held accountable. Therefore, a Muslim should repel these thoughts by remembering Allah.