It is narrated from Sayyiduna Abu Mas'ud (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "No animal should be sacrificed whose ear is cut at the front, nor one whose ear is cut at the back, nor one whose ear is slit, nor one whose ear is pierced." And the Messenger of Allah (peace and blessings be upon him) commanded us to examine the eye and the ear (of the sacrificial animal) carefully.
Hadith Referenceالمعجم الكبير للطبراني / باب العين / 14748