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]. (JA)
App reference (JA): Book 18, Hadith 61 (JA)
Arabic/English book reference (JA): Book 18, Hadith 1571 (JA)