Musannaf Ibn Abi Shayba 18:1207

Abu Bakr narrated to us, he said: Ibn ‘Ulayyah narrated to us, from Khalid, from Abu Qilabah, from Abu al-Ash’ath, from Shaddad ibn Aws, who attributed it (to the Prophet), he said: "Indeed, Allah has prescribed excellence (ihsan) upon you in everything. So if you kill, then perform the killing with excellence, and if you slaughter, then perform the slaughter with excellence."