It was narrated from Abu Hurairah that:
the Messenger of Allah (ﷺ) said: "Allah has forgiven my nation for what they think of to themselves, so long as they do not act upon it or speak of it." (ID)
English reference (ID): Vol. 3, Book 10, Hadith 2040 (ID)
Arabic reference (ID): Book 10, Hadith 2118 (ID)