Narrated Abu Idris Al-Khawlani:
"When 'Umar bin Al-Khattab removed 'Umair bin Sa'd as governor of Hims, he appointed Mu'awiyah. The people said: 'He has removed 'Umair and appointed Mu'awiyah.' So 'Umair said: 'Do not mentioned Mu'awiyah except with good, for indeed, I heard the Messenger of Allah (ﷺ) saying: "O Allah guide (others) by him." (JA)
English reference (JA): Vol. 1, Book 46, Hadith 3843 (JA)
Arabic reference (JA): Book 49, Hadith 4214 (JA)