`Sayyiduna Jabir bin Abdullah (may Allah be pleased with him) reports that the Messenger of Allah (peace and blessings be upon him) said: Do not slaughter (for sacrifice) except a musinnah (an animal that has completed one year and entered the second, i.e., a two-toothed animal), but if you cannot find such an animal, then sacrifice a jadha’ of sheep (one that has completed six months and entered the seventh).