Sinning in seclusion
Hadhrat Thawbaan (Radhiallahu anhu) reports that Rasulullah ﷺ said, “I know of a group of my Ummah will come with good deeds on the Day of Judgment like a Mountain. Allah will scatter their deeds like dust(their deeds will hold ne value).
Thawbaan (Radhiallahu anhu) exclaimed, “Give us their full description so that we may never be from amongst them out of ignorance!”
Rasulullah ﷺ replied, “they will be your brothers, from your own tribes. They will worship Allah by night just as you do. But they are such people that when they are tempted with sin in privacy, they commit what Allah has forbidden. (ibn Majah)