Good Manners and Form (Al-Adab)
Ṣaḥīḥ al-Bukhārī 6069
كُلُّ أُمَّتِي مُعَافًى إِلاَّ الْمُجَاهِرِينَ، وَإِنَّ مِنَ الْمَجَانَةِ أَنْ يَعْمَلَ الرَّجُلُ بِاللَّيْلِ عَمَلاً، ثُمَّ يُصْبِحَ وَقَدْ سَتَرَهُ اللَّهُ، فَيَقُولَ يَا فُلاَنُ عَمِلْتُ الْبَارِحَةَ كَذَا وَكَذَا، وَقَدْ بَاتَ يَسْتُرُهُ رَبُّهُ وَيُصْبِحُ يَكْشِفُ سِتْرَ اللَّهِ عَنْهُ
kullu ummatī muʿāfan illā al-mujāhirīna, wa-inna mina al-majānah an yaʿmala ar-rajulu bi-l-layli ʿamalan, thumma yuṣbiḥa waqad satarah Allāh, fayaqūla yā fulānu ʿamiltu al-bāriḥaha kadhā wakadhā, waqad bāta yasturuhu rabbuhu wayuṣbiḥu yakshifu sitra-Llāh ʿanhu
Transliteration generated from the Arabic vowel marks
The full narration
Narrated Abu Huraira:I heard Allah's Messenger (ﷺ) 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
Source
Ṣaḥīḥ al-Bukhārī · 6069