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." (ES)
English reference (ES): Vol. 3, Book 10, Hadith 2040 (ES)
Arabic reference (ES): Book 10, Hadith 2118 (ES)