From Sahih Muslim (Hadith 4526):
It has also been narrated by Sa'd b. Abu Burda through his father through his grandfather that the Prophet of Allah (ﷺ) sent him and Mu'adh (on a mission) to the Yemen, and said (by way of advising them):Show leniency (to the people) ; don't be hard upon them; give them glad tidings (of Divine favours in this world and the Hereafter) ; and do not create aversion. Work in collaboration and don't be divided
Reference: Muslim 4526