What defects disqualify an animal designated for sacrifice (Hady)?
Chapter on Ransom (Fidyah) and Penalty for Hunting
Al-Mughni
Book of Hajj
Primary text
The same defects that disqualify an animal offered as a ritual sacrifice (Udhiyah) also disqualify the Hady animal. The Prophet Muhammad (peace be upon him) stated that four types of animals are invalid for sacrifice: the obviously one-eyed animal, the clearly sick animal, the obviously lame animal, and the emaciated animal lacking marrow. This ruling is supported by Al-Bara' ibn 'Azib and the jurist 'Ata'. The explicitly mentioned defects are total blindness of one eye (where the eyeball is gone), severe lameness preventing movement with the herd and feeding, and emaciation due to lack of marrow. Sickness that affects the leanness of the animal or corrupts its meat also disqualifies it. There is no known disagreement among scholars regarding the prohibition of these four defects.
Supporting text
The obvious reading of the Hadith implies that any sickness significantly affecting the animal's meat or causing it to become lean is disqualifying. Furthermore, defects exceeding these four in severity are prohibited by necessary implication, such as total blindness (which is worse than one-eyedness) or the removal of a desirable part like the tail (Aliyah), as this impairs the intended purpose more severely than the loss of the fat pad of the eye.