Sayyiduna Buraydah (may Allah be pleased with him) narrates: We prayed the Zuhr prayer behind the Messenger of Allah (peace and blessings be upon him). When he (peace and blessings be upon him) finished his prayer and turned around, he faced us in a state of anger and called out in a voice that even the young maidens could hear from within their curtains, and said: "O you who have accepted Islam but faith has not yet entered your hearts! Do not find fault with the Muslims, and do not seek out their faults, for whoever pursues the fault of his Muslim brother, Allah tears away his cover and exposes his fault, even if he is inside his own house."
Hadith Referenceالمعجم الكبير للطبراني / باب الباء / 1144