It's like Saving a girl from Being Buried Alive (Hide Other's faults)

Allah's Apostle said:

ومن ستر مسلما ستره الله في الدنيا والآخرة والله في عون العبد ما كان العبد في عون أخيه

"He who conceals (the faults) of a Muslim, Allah would conceal his faults in the world and in the Hereafter. Allah is at the back of a servant so long as the servant is at the back of his brother."
[Hadith 1245: Muslim]

The Prophet also said:

من ستر عورة مؤمنٍ فكأنَّما استحيا موءودةً من قبرها

"He who sees something which should be kept hidden and conceals it, it will be like the one who has brought to life (saved) a girl buried alive."
[Hadith 2292: Abu Dawud]