In the Name of Allah, The Most Gracious, Most Merciful
The condition of the Udhiyah:
One of the conditions of the Udhiyah (an animal of the an'aam class (i.e., camel, cow, sheep or goat) that is slaughtered during the days of Eid Al-Adha because of the Eid, and as an act of worship, intending to draw closer to Allah thereby) is Al-Yasaar (having enough money), and the Muwsser is the one who is eligible to pay Zakat, so he has money more than what is needed to meet his basic needs, the one who does not need the price of the Udhiyah during the days of Eid Al-Adha only or the one who does not need the price of Al-Udhiyah during the whole year, according to opinions of the School of Thoughts concerning the definition of Al-Muwsser.
Al-Udhiyah should not suffer from any serious disease that causes the loss of some of its meat or that causes harm when eating its meat. Thus, it is not permitted to sacrifice an animal that is seriously and obviously sick, nor is it permissible to sacrifice the one-eyed animal, the lame animal, the very thin animal and the one which suffers from scabies. Hence, it is desirable to choose the fattest and the best animal. The Prophet, peace be upon him, used to sacrifice a horned white ram.