People do not get their nails and hair cut during these 10 days. Is it correct that if we cut our nails and hair we will be sinful?

The basic Shar'i ruling: For a person who intends to offer the sacrifice, cutting the hair of any part of the body, the nails, or the skin, from the sighting of the moon of Dhul-Hijjah until the sacrificial animal has been slaughtered, is forbidden and haram in the Shariah. If someone cuts them deliberately without an excuse, he will be sinful; he should repent and seek forgiveness, although his sacrifice does not thereby become invalid.

The evidence: The narrations of Sahih Muslim reported from Sayyidah Umm Salamah, may Allah be pleased with her: "When the tenth day of Dhul-Hijjah (i.e. its moon) begins and one of you intends to offer a sacrifice, he should not cut anything from his hair and his nails"; and in another narration: "He should not touch his hair or his skin at all." The word "fala ya'khudhanna" (he must not take) is a prohibition, and an explicit prohibition indicates unlawfulness (tahrim); the imams (Imam Ahmad, Ishaq ibn Rahwayh, Sa'id ibn al-Musayyab) regard it as haram and a sin.

Clarifying points: The restriction applies only to the actual owner of the sacrifice, not to the other members of the household. If someone cuts them forgetfully or out of ignorance, there is no sin and no fidyah is due. Cutting in a case of severe need (a broken nail, a wound) is permissible — prohibited things become permissible at the time of necessity.

Summary: For the one offering the sacrifice, cutting hair and nails during these ten days without an excuse is impermissible and a sin; if it happens, he should seek forgiveness, and the sacrifice will remain valid.

Translated from the original Urdu fatwa.