It is narrated from Sayyiduna Shaddad bin Aws (may Allah be pleased with him); he said: There are two things that I heard from the Prophet (peace and blessings be upon him); he (peace and blessings be upon him) said: "Indeed, Allah has prescribed excellence (ihsan) in everything. So when you kill, kill in a good manner, and when you slaughter, slaughter in a good manner; and let one of you sharpen his blade, and let him give ease to the animal he slaughters."
Hadith Referenceالمعجم الكبير للطبراني / باب الشين / 7084