Abu Dawud

Hadith Commentary:
On the occasion of the Farewell Pilgrimage (Hajjat al-Wada‘), after completing the rites of Hajj, the Messenger of Allah (sallallahu alayhi wa sallam) had his blessed head shaved, and for those Companions who had their heads shaved, he supplicated for mercy and grace for them three times, while for those who had their hair cut short, he supplicated only once.

There is no evidence that the Messenger of Allah (sallallahu alayhi wa sallam) ever had his head shaved except during Hajj and ‘Umrah; rather, he kept his hair with great honor and respect.

His hair would sometimes reach his ears and sometimes be level with his neck.

When it grew long, his hair would take the form of plaits.

Since these ahadith mention the Farewell Pilgrimage (Hajjat al-Wada‘), Imam Bukhari (rahimahullah) has mentioned them here.

Hadith Commentary:
It is understood that shaving the head or cutting the hair is also one of the acts of Hajj.

Hadith Commentary:
(1)
Abdullah ibn Umar (radi Allahu anhu) intended to perform Hajj in the year when Hajjaj ibn Yusuf launched a military campaign against Abdullah ibn Zubair (radi Allahu anhu). Ibn Umar (radi Allahu anhu) entered into the state of ihram, and continued in it until the tenth of Dhu al-Hijjah, when he offered the sacrifice and shaved his head. Then he said that the Messenger of Allah (sallallahu alayhi wa sallam) had done the same during his Hajj.
(Sahih Muslim, Book of Hajj, Hadith: 2992(1230))

(2)
From this hadith, Imam Bukhari (rahimahullah) has established the permissibility of shaving the head when exiting the state of ihram, while in the chapter heading he also mentions trimming the hair. Accordingly, in some narrations it is mentioned that the Prophet (sallallahu alayhi wa sallam) and his noble Companions (radi Allahu anhum) shaved their heads, and some individuals trimmed their hair.
(Sahih al-Bukhari, Book of Expeditions, Hadith: 4411)
However, it is not permissible for women to shave their heads; rather, they should take a few hairs from their braid. Thus, it is narrated from Ibn Abbas (radi Allahu anhu) that the Messenger of Allah (sallallahu alayhi wa sallam) said:
“For women, there is no shaving of the head, only trimming.”
(Sunan Abi Dawud, Book of Rituals, Hadith: 1984)
In any case, at the conclusion of Hajj or Umrah, shaving the head is superior for men, and trimming is permissible, as will be made clear in the forthcoming ahadith.

Hadith Commentary: Benefits and Issues: Shaving the head is, by consensus, superior to cutting the hair, and shaving (halq) and shortening (taqsir) are among the acts of worship in Hajj.

The correct opinion of the four Imams is that, in order to exit the state of ihram, shaving or shortening is obligatory.

According to Imam Malik rahimahullah, Imam Abu Hanifah rahimahullah, and Ishaq rahimahullah and others, if someone shaves or shortens the hair after exiting ihram, then he will have to offer the sacrifice of an animal.

According to Imam Shafi'i rahimahullah, Imam Ahmad rahimahullah, and Abu Yusuf rahimahullah, one can shave or shorten the hair until the last day of sacrifice; if he delays even beyond this, then according to Imam Ahmad rahimahullah, a compensatory sacrifice (dam) will be required.

According to Imam Ahmad rahimahullah and Imam Malik rahimahullah, shaving the entire head is obligatory.

According to Imam Abu Hanifah rahimahullah, shaving a quarter of the head is obligatory.

According to Imam Shafi'i rahimahullah, shaving three hairs is obligatory.

However, the practice of the Prophet sallallahu alayhi wa sallam is our example: he sallallahu alayhi wa sallam had his entire head shaved, and during ‘umrah he also had all his hair cut. For women, shaving the head is impermissible.

However, it is permissible for them to cut a few hairs, and in shaving, according to all the Imams except Imam Abu Hanifah rahimahullah, it is recommended to begin with the right side of the head. If someone does not have hair on his head, then a razor should be passed over his scalp.