What are the rules for animal sacrifice during حج?

The animal sacrifice (hady) is واجب (wajib) for حجاج performing حج Tamattu (those who perform عمرہ, exit احرام, then enter احرام again for حج) and حج Qiran (those who combine عمرہ and حج in a single احرام). Pilgrims performing حج Ifrad (حج only, without عمرہ) are not required to offer a sacrifice, though it is مستحب.

Acceptable animals include: a sheep or goat (one per حاجی), a cow (shared among up to 7 حجاج), or a camel (shared among up to 7 حجاج). The animal must meet minimum age requirements — sheep must be at least 6 months old, goats 1 year, cows 2 years, and camels 5 years. The animal should be healthy and free from defects: not blind in one eye, not obviously lame, not emaciated, and not missing a significant portion of an ear or horn.

The sacrifice should ideally be performed on the 10th of Dhul Hijjah (Yawm al-Nahr — Day of Sacrifice), as part of the day's sequence: stoning, then sacrifice, then shaving/trimming, then طواف. However, the sacrifice may be delayed until before sunset on the 13th of Dhul Hijjah. Most حجاج today arrange their sacrifice through the Saudi Project for Utilization of Hady and Udhiyah (the official sacrifice management organization), which handles the slaughter and distributes the meat to the poor worldwide. You simply pay the fee and receive a certificate confirming the sacrifice was performed.