Sayyiduna Abu Layla al-Ash'ari (may Allah be pleased with him) said that the Messenger of Allah (peace and blessings be upon him) said: "Hold firmly to obedience to your rulers and do not oppose them, for obedience to them is obedience to Allah and disobedience to them is disobedience to Allah. Indeed Allah has sent me to call to His path with wisdom and good admonition, so whoever succeeds me in that is from me and I am from him."
Hadith Referenceالمعجم الكبير للطبراني / مسند من يعرف بالكنى / 19139