A pilgrim on hajj or 'umra shaving his head for himself or for another
There is no objection to a pilgrim performing 'umra to shave his head or shorten his hair for himself or for others who are eligible to do this after finishing sa'y [traversing between as-Safa and al-Marwa]. Likewise, there is no objection to a pilgrim performing hajj from doing the same after departing from Muzdalifah for Mina. Rather, a pilgrim is commanded to shave his head or shorten his hair by virtue of the general implication of legal texts. Allah the Almighty says,
You will surely enter al-Masjid al-Haram, if Allah wills, in safety, with your heads shaved and [hair] shortened. [Al-Fat-h: 27]
In a hadith included in the Sahih Of Bukhari and the Sahih of Muslim through Abdullah ibn Umar (may Allah be pleased with them both) the Prophetsaid, "May Allah have mercy upon those who shavetheir heads, may Allah have mercy on those who shave their heads, may Allah have mercy on those who shave their heads and on those who shorten their hair" (this is an abridged version of the hadith).
If we deem it impermissible for a pilgrim on 'umra or hajj to shave his own head or for others, we would oblige him to depend on non-muhrims [a muhrim is a person in a state of ihram—the state of consecration that a pilgrim enters for hajj or 'umra] in shaving his head and shortening his hair. This would make him dependent on others to perform this act of worship; other acts of worship are devoid of such a dependency. A Muslim praying does not need others to perform prayers. Likewise, a person who is fasting or a zakat-payer does not need others to perform these acts of worship.
Scholarly transmissions are free from the obligation of resorting to non-muhrims for this rite. Had it been a condition, scholars would have mentioned it. Rather,what is required, is that the rite be done by oneself or by another who is either a muhrim or a non-muhrim.
Whether we maintain that shaving the head and shortening the hair is an act of worship or one that makes an unlawful act lawful according to the two opinions of the Shafi's, the ruling remains the same: it is permissible for a muhrim to shave his head for himself or for other muhrims at this stage of their rites. This is based on the fact that at this stage of the rites, shaving or shortening the hair has become lawful after it was forbidden. Therefore, it takes precedence over performing a permissible action such as shaving for a non-muhrim. Al-Nawawi stated in Rawdat al-Talibeen, "It is permissible for a muhrim to shave the head of a non-muhrim." Whoever maintains the impermissibility of a pilgrim on 'umra or hajj shaving his head or trimming his hair should know that, while it is true that removing hair from the body is among the restrictions of ihram, yet this prohibition applies only up to a certain stage of the rites. Once past this stage, a muhrim is required to release himself from ihram by shaving his head or shortening his hair, rendering lawful everything that was unlawful to him during ihram for umra, some of the things that were unlawful for him before the partial release for ihram for hajj or most of the things that were unlawful for him before full release from ihram for hajj.