"The Messenger of Allah commanded us to examine the eyes and ears (of animals) and not to Sacrifice and animal with a bad eye, nor an animal with its ears slit from the front, nor an animals with its ears slit form the back, nor an animal with a round hole in its ear.  

أَمَرَنَا رَسُولُ اللَّهِ ﷺ أَنْ نَسْتَشْرِفَ الْعَيْنَ وَالأُذُنَ وَأَنْ لاَ نُضَحِّيَ بِعَوْرَاءَ وَلاَ مُقَابَلَةٍ وَلاَ مُدَابَرَةٍ وَلاَ شَرْقَاءَ وَلاَ خَرْقَاءَ