If someone else performs the Adhha sacrifice for a Person, can he shave his Hair or not?

Question :

A person wants a man to perform the Adhha sacrifice for him and the first 10 days of Thul-Hijjah have begun. Therefore, is it permissible for these two people to remove any of their hair or is it permissible for one of them and not permissible for the other or is it not permissible for both of them? And what is the ruling concerning a person who lost his sheep that he intended to sacrifice for the Adhha sacrifice, then he finds it after the days of slaughtering are over?

Answer:

It is reported in the authentic Hadith:
"When the month of Thul-Hijjah enters and one of you wants to perform an Adhha sacrifice, he should not remove anything from his hair or his nails or his skin. "

The Prophet did not mention the person who has someone other than himself perform the Adhha sacrifice for him. However, some of the scholars considered it (removing hair, etc.) also disliked for the person who has someone else perform the sacrifice for him. Yet, whoever removes some of his hair is not required to offer a ransom of atonement and his Adhha sacrifice is not nullified nor should he leave off the sacrifice. It is accepted from him if Allâh wills.

If the person decides to perform the Adhha sacrifice and he buys it, but then he loses the animal and cannot find it until after the days of slaughter are over, he is not required to slaughter it, unless it was an obligation under his responsibility, by a vow or a specific stipulation. If he still slaughters it in this situation and gives its meat away in charity like the Adhha sacrifice, he gets reward if Allâh wills. If he slaughtered another animal in its place during the days of the 'Eid, he is not required to slaughter another.

Source:
Ash-Shaykh Ibn Jibreen
Fatawa Islamiyah, Vol. 4 Pages 325-326