Show leniency (to the people), don't be hard upon them, give them glad tidings (of Divine favors in this world and the Hereafter), and do not create aversion. Work in collaboration and don't be divided.

Muslim :: Book 19 : Hadith 4298 [Messenger of Allah (peace and blessings be upon him) giving instructions to Muadh bin Jabal (may Allah swt please with him) while sending him as ambassador to Yemen]