The Messenger of Allah ﷺ said, "Whoever conceals the faults of a Muslim, Allah will conceal his faults in this world and the next."
حدثنا أبو بكر بن أبي شيبة حدثنا أبو معاوية عن الأعمش عن أبي صالح
قال رسول الله ﷺ من ستر مسلما ستره الله في الدنيا والآخرة
Muslim narrated it in the Book of Remembrance and Supplication, Chapter on the virtue of gathering to recite the Quran and to make remembrance, h: 2699, from the hadith of Abu Bakr bin Abu Shayba, at greater length. See h: 225 of this book.