Taqsir or Halq
Taqsīr (التَقصير) or ḥalq (الحلق) is one the obligations of ḥajj and ʿumra. Taqsīr involves cutting some strands of the hair from head, beard, mustache, or alternatively one may cut a nail of hand or foot. Ḥalq means shaving one's head, which is only permissible for men.
Taqsīr or ḥalq, like other rituals is an act of worship in ʿumra. So, it is obligatory that one should make the right intention.
In ʿUmra
In ʿumra the fifth deed after saʿy is taqsīr. In al-ʿumra al-mufrada halq is acceptable instead of taqsīr, but in ʿumra al-tamattuʿ a man is not permitted to perform halq and it is obligatory for him to only perform taqsīr.
Ḥalq (shaving head) is not permissible, nor sufficient to exit the state of iḥrām in ʿumra al-tamattuʿ. One must perform taqsīr so as to complete ʿumra al-tamattuʿ and exit the state of iḥrām. If a person shaves his head purposely and knowingly before or after taqsīr he must slaughter a sheep as kaffāra.
Plucking hair is not sufficient to exit iḥrām of ʿumra al-tamattuʿ; one should perform taqsīr as mentioned. If he plucks his hair instead of taqsīr deliberately and knowingly, it is not sufficient, moreover, he has to pay kaffāra for it. If a person plucks his hair instead of doing taqsīr unknowingly and then performs ḥajj al-tamattuʿ, his ʿumra is void and the performed ḥajj will be considered as ḥajj al-ifrād. If ḥajj was obligatory for him, on the basis of obligatory caution, he should perform al-ʿumra al-mufrada after performing the rites of ḥajj and the next year, he has to perform ʿumra al-tamattuʿ and ḥajj al-tamattuʿ. The same ruling applies to a person who has shaved his head instead of taqsīr and then performed ḥajj unknowingly.
It is not obligatory to do taqsīr directly after performing saʿy. If a person does not perform the act of taqsīr deliberately or ignorantly and without it he wears iḥrām for ḥajj, his ʿumra would be void and his ḥajj would be considered as ḥajj al-ifrād. On the basis of obligatory caution, he should perform al-ʿumra al-mufrada after performing ḥajj and if his ḥajj was obligatory, he should perform ʿumra and ḥajj the next year. If a person neglects taqsīr inadvertently and wears iḥrām for ḥajj, his iḥrām would be valid as well as his ʿumra and ḥajj, and kaffāra is not obligatory for him. However, it is mustahabb to slaughter a sheep or goat as kaffāra. Rather, it is a caution not to neglect paying kaffāra.
After performing taqsīr and exiting the state of iḥrām of ʿumra al-tamattuʿ, every forbidden thing in state of iḥrām becomes halal including intercourse with one's spouse.
In Hajj
Taqsīr (التَّقصير) or ḥalq is the sixth obligation of ḥajj and formulates the third rite at Minā. It is obligatory to do ḥalq or perform taqsīr after slaughtering an animal.
Women should perform taqsīr, as ḥalq is not adequate for them. It is based on caution that they should shorten some of their hair and nails. Men are allowed to choose between ḥalq and taqsīr. Shaving head is not obligatory for them but if they are performing ḥajj for the first time, on the basis of obligatory caution, they should shave their head.
Both ḥalq and taqsīr are acts of worship. It is obligatory to have pure intention for seeking nearness of Allah Almighty and it should be free from any sort of rīyā (people pleasing tendency). So, if a person performs ḥalq or taqsīr without the conditions required for intention, ḥalq and taqsīr would not be sufficient and the things permission of which depends on ḥalq and taqsīr would not become permissible for him.
If a person seeks help from others in performing taqsīr or ḥalq, he must do intention himself.
It is based on obligatory caution, ḥalq or taqsīr should be performed on the day of Eid al-Adha or else it must be performed on the night before the 11th day or it would be sufficient to do it any time after that. For a person, who delays slaughtering of animal due to any reason and do not perform it on the day of Eid, it is not necessary to delay ḥalq or taqsīr. On the basis of obligatory caution, performing ḥalq and taqsīr is mandatory on the day of Eid al-Adha. However, performing the ṭawāf of ḥajj and the other five ritual deeds in the Holy city of Mecca in this state are objectionable. He should wait and perform these deeds after slaughtering the animal.
Ḥalq or taqsīr must be performed in the land of Minā i.e. performing these rites in other places by choice is not allowed. If a person performs ḥalq or taqsīr outside the land of Minā deliberately, forgetfully or ignorantly, or goes out of Minā without taqsīr and ḥalq and performs all the deeds, it is obligatory to return to Minā for ḥalq and taqsīr and then repeat the following rites.
On the day of Eid al-Adha, it is obligatory to perform ramy (stoning) at Jamara al-ʿAqaba first, slaughter an animal if the animal for slaughtering is feasible for him, followed by taqsīr or ḥalq. If a person disturbs the order of rites deliberately, he/she has committed disobedience. Apparently, it is not obligatory for him/her to repeat these acts although it is compatible with caution to repeat these rites, if possible. This ruling also applies to a person who does not abide by the specific order of rites due to ignorance and forgetfulness.
If a person is unable to slaughter the animal on the day of Eid al-Adha at Minā, but it is possible to slaughter it in the current slaughterhouse situated outside Minā, it is based on obligatory caution to slaughter his/her animal and then perform ḥalq or taqsīr. In case, if this deed is impossible for him, on the basis of obligatory caution, he/she should do ḥalq or taqsīr on the day of Eid al-Adha and by doing so, the person would become free from state of iḥrām. However, he/she should delay fulfillment of five rites in the holy city of Mecca until the slaughtering of animal or else the validity of these rites is objectionable.
After doing ḥalq or taqsīr, all the things that were forbidden for a muḥrim will become permissible for him except his/her spouse and scent.