From Sahih Bukhari (Hadith 3038):
Narrated Abu Burda:That his father said, "The Prophet (ﷺ) sent Mu`adh and Abu Musa to Yemen telling them. 'Treat the people with ease and don't be hard on them; give them glad tidings and don't fill them with aversion; and love each other, and don't differ
Reference: Bukhari 3038