Sayyiduna Shaddad bin Aws (may Allah be pleased with him) narrates from the Prophet (peace and blessings be upon him): "Allah, the Lord of Might, is excellent in doing good; He has prescribed excellence (ihsan) in everything. When you kill, kill in a good manner, and when you slaughter an animal, sharpen the knife so that the animal may be given ease."
(b) Sayyidah Aishah (may Allah be pleased with her) narrates from the Prophet (peace and blessings be upon him) that when a ram was brought to be sacrificed, he (peace and blessings be upon him) said: "O Aishah! Bring the knife and sharpen it on a stone."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الضحايا / 19138