Question:
I intended to fulfill the obligation of Hajj and want to clip nails and shave my hair before I set out, but the month of Thul-Hijjah has already started. Would I be sinning if I do?
Answer:
All perfect praise be to Allah, The Lord of the worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.
Shaving the hair or clipping the nails is forbidden only for a person who has already assumed Ihraam for Hajj or ‘Umrah. If, for example, one assumes Ihraam on the eighth day of Thul-Hijjah, then he is forbidden to shave his hair and clip his/her nails. Before that date, one is not forbidden to shave his hair or clip his/her nails. Some scholars say that shaving hair and clipping nails is a recommended act when wanting to assume Ihraam. However, people who intend to slaughter Udh-hiyah (both pilgrims in the state of Ihraam and others) are forbidden from this starting from the beginning of Thul-Hijjah. Shaafi‘i scholars argue that this forbiddance implies being not recommended; whereas Hanbali scholars argue that it implies unlawfulness. It is narrated on the authority of Umm Salamah, may Allah be pleased with her, that the Prophet said, “When the [first] ten days of Thul-Hijjah commence and anyone of you intends to offer a sacrificial animal (Udh-hiyah), should not touch his hair (i.e. trim it, cut it or shave it) nor clip his nails.” [Muslim]
Allah Knows best.