The Prophet ﷺ sent Muaz and Abu Musa to Yemen and said to them, "Make things easy and do not make them difficult, give glad tidings and do not drive people away, and cooperate with one another and do not differ."
ى، أن النبي ﷺ بعث معاذا وأبا موسى إلى اليمن، قال: يسرا ولا تعسرا، وبشرا ولا تنفرا، وتطاوعا ولا تختلفا.
Bukhari related it in jihad (3038), and Muslim in jihad and expeditions (1733), both of them by way of Waki, from Shuba, from Saeed bin Abu Burda, from his father, from his grandfather, and he mentioned it. And His saying, "He named you Muslims before" [Hajj 22:78]