Anas bin Malik reported,
The Messenger of Allah ﷺ said, "When you judge, judge with justice. When you must kill, do so with excellence, for Allah 
is excellent and loves those who act with excellence."
Azami 7199
Hasanعن أنس قال
قال رسول الله ﷺ: إذا حكمتم فاعدلوا، وإذا قتلتم فأحسنوا، فإن الله عز وجل محسن، يحب المحسنين.
No references are available.
Ibn Abu Asim narrated it in al-Diyat (184), Tabarani in al-Awsat, Majma al-Bahrayn (2552), and Abu Naeem in Akhbar Isbahan (2/113), all of them through various routes from Muhammad bin Bilal, who said, Imran Qattan told us, from Qatada, from Anas, and he related it. Its isnad is hasan because of Muhammad bin Bilal Basri Tammar and his teacher Imran bin Dawwar Qattan, for both of them make the hadith hasan.Haythami said in al-Majma (1975), "Tabarani narrated it, and its narrators are trustworthy."