question #1 Sahih al-Bukhari 4919, Book 65, Hadith 439 : What is the significance of sincerity in worship and its impact on the Day of Judgment?

I heard the Prophet (ﷺ) saying, “Our Lord Allah will lay bare His Shin, and then all the Believers, men and women, will prostrate themselves before Him, but there will remain those who used to prostrate in the world for showing off and for gaining good reputation. Such people will try to prostrate (on the Day of Judgment) but their back swill be as stiff as if it is one bone (a single vertebra).