Muawiyah (May Allah be pleased with him) said:
I heard the Messenger of Allah (ﷺ) saying, "If you find faults with Muslims, you will corrupt them."[Abu Dawud]. (RU)
App reference (RU): Book 18, Hadith 61 (RU)
Arabic/English book reference (RU): Book 18, Hadith 1571 (RU)