What are the rules for animal sacrifice during الحج?

The animal sacrifice (هدي) is واجب (واجب) for الحجاج performing الحج Tamattu (those who perform العمرة, exit الإحرام, then enter الإحرام again for الحج) and الحج Qiran (those who combine العمرة and الحج in a single الإحرام). Pilgrims performing الحج Ifrad (الحج only, without العمرة) are not required to offer a sacrifice, though it is مستحب.

Acceptable animals include: a sheep or goat (one per الحاج), a cow (shared among up to 7 الحجاج), or a camel (shared among up to 7 الحجاج). 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 ذو الحجة (يوم النحر — Day of Sacrifice), as part of the day's sequence: stoning, then sacrifice, then shaving/trimming, then الطواف. However, the sacrifice may be delayed until before sunset on the 13th of ذو الحجة. Most الحجاج 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.