Narrated by Abu Huraira (Radi-Allahu 'anhu):

I heard Allah's Apostle (Sallallahu 'Alaihi Wa Sallam) saying. "All the
sins of my followers will be forgiven except those of the Mujahirin (those
who commit a sin openly or disclose their sins to the people). An example
of such disclosure is that a person commits a sin at night and though Allah
screens it from the public, then he comes in the morning, and says, 'O
so-and-so, I did such-and-such (evil) deed yesterday,' though he spent his
night screened by his Lord (none knowing about his sin) and in the morning
he removes Allah's screen from himself."

Bukhari Vol. 8 : No. 95