Sayyiduna al-Miqdad bin al-Aswad and Sayyiduna Abu Umamah (may Allah be pleased with them both) narrate from the Prophet (peace and blessings be upon him) that he (peace and blessings be upon him) said: "Indeed, when the imam (ruler) seeks out tribulation among the people, he corrupts them."
Hadith Referenceالمعجم الكبير للطبراني / باب الميم / 17741