All perfect praise be to Allah the Lord of the Worlds. May His peace and blessings be upon Prophet Mohammad and upon all his family and companions.

Ihsar is one of the obstacles to completing Hajj after starting it. It is of two types: 

general and specific. As for the general Ihsar, it refers to the prevention of pilgrims from proceeding to complete Hajj or Umrah by an enemy blocking all paths. Imam Al-Sharbini, may Allah have mercy on him, said: "It does not matter whether the prevention is by cutting off the road or through other means, and whether the one preventing is a disbeliever or a Muslim" [Mughni Al-Muhtaj, vol. 2/pp. 313].

It is permissible for someone prevented (Muḥṣar) from completing Hajj or Umrah to exit the state of Iḥrām. This is done through three things: intention—by intending to exit Iḥrām, the sacrifice of a sheep where they were prevented, whether in the Ḥaram or outside, and shaving the head, as Allah The Exalted Says (What means): "But if you are prevented, then [offer] what can be obtained with ease of sacrificial animals." [Al-Baqarah/196]. The requirement of a sacrificial offering is not waived if they had stipulated upon entering Iḥrām that they would exit Iḥrām if prevented, because exiting due to prevention is permissible without such a condition, thus rendering the condition void.

As for specific prevention (Haṣr Khāṣṣ), it applies to someone who is unjustly detained, such as being imprisoned for a debt they are unable to repay. In such a case, it is permissible for them to exit Iḥrām, just as is the case with general prevention (Haṣr 'āmm).

The pilgrimage or Umrah that was missed due to prevention, whether general or specific, could be obligatory or voluntary. Missing a voluntary pilgrimage does not require making it up. Shaykh al-Islam Imam Ibn Hajar Al-Haytami, may Allah have mercy on him, said: "There is no obligation to make up a voluntary pilgrimage for someone prevented (from completing it), whether it is due to specific or general prevention, even if it leads to missing the pilgrimage, as there is no command requiring it" [Tuhfat Al-Muhtaj, vol. 4/pp. 211].

As for an obligatory pilgrimage that was missed due to being prevented (i.e., Iḥṣār), it may either be a firmly established obligation—meaning the conditions of ability had been met before the year in which one was prevented—or not. If it is a firmly established obligation—such as making up for a missed Hajj, the Hajj of Islam after the first year of capability, or a vowed Hajj that one was able to fulfill before the year of prevention—it remains a debt upon the individual, and they are required to make it up. However, if the obligation was not firmly established—such as being in the first year of ability to perform the Hajj—then there is nothing required of him until he becomes capable again.

Imam Al-Nawawi, may Allah have mercy on him, said: "If the person prevented from completing Hajj (Iḥṣār) releases themselves from their state of Iḥrām, then according to Al-Shafi'i, Al-Shirazi (author of Al-Muhadhdhab), and the other scholars: if the pilgrimage was voluntary, there is no requirement to make it up. However, if it was obligatory, there are two scenarios: If the obligation was already established—such as a make-up Hajj, a vowed Hajj, or the Hajj of Islam that became obligatory before that year—the obligation remains upon him, and being prevented only allows him to exit from Iḥrām. If it was an obligation that was not yet established, such as the Hajj of Islam in the first year of ability, then the requirement is dropped due to the loss of capability. No Hajj is required of him unless the conditions of ability are met in the future." [Al-Majmu' Sharh Al-Muhadhdhab, vol.8 /pp. 306].

As for the case when a pilgrim falls ill, it is not permissible for them to exit their state of Iḥrām due to illness. They must remain patient until they recover, as exiting Iḥrām does not remove the illness, unlike the case of Iḥṣār. If the ill pilgrim is performing Umrah, they should complete it. However, if they are performing Hajj and they miss the standing at Arafah, they should exit their Iḥrām by performing the acts of Umrah—which include Tawāf, Sa‘y, and shaving the head. This applies if they did not make a condition at the time of Iḥrām to exit in the event of illness. If they did make such a condition, it is valid, and they are allowed to exit Iḥrām. This is based on the hadith narrated by our mother, Aisha (may Allah be pleased with her), who said: "The Prophet (peace be upon him) entered upon Ḍubā‘ah Bint Al-Zubayr Ibn ‘Abd Al-Muṭṭalib, and she said: "O Messenger of Allah, I wish to perform Hajj, but I am unwell.' The Prophet (peace be upon him) replied: "Perform Hajj and make the condition that your place of exiting Iḥrām will be wherever you are stopped by the illness." (Agreed upon). Imam Al-Nawawi (may Allah have mercy on him) said: "This hadith indicates that illness does not permit exiting Iḥrām unless a condition was made at the time of entering Iḥrām." [Shariḥ Ṣaḥīḥ Muslim,vol. 8/pp.132]. If the pilgrim made a condition for exiting with a sacrificial offering, then it is obligatory upon them; otherwise, it is not. If the condition was left unspecified, no sacrificial offering is required due to the absence of a condition, in line with the hadith of Ḍubā‘ah. Thus, the exit from Iḥrām for someone who did not specify a sacrificial offering, or left the condition general, is completed with intention and shaving only. If the pilgrim performing Hajj stipulated that their Hajj should convert to Umrah in case of an excuse, and the excuse occurred, then their Hajj converts to Umrah and it suffices for Umrah Al-Islam. This is not the case with Iḥṣār, where the acts performed do not suffice for Umrah al-Islam, as they are not considered a true Umrah, but merely the acts of Umrah.

As for the obligation to make up for the missed Hajj, if the missed Hajj of the ill person was obligatory, it remains as a duty upon them just as it was. If it was voluntary, they are required to make it up immediately, just as if they had invalidated it. In both cases, a sacrificial offering is also required when making up for the missed Hajj.

The definition of illness, in this context, is that which permits the person to skip the Friday prayer (Jum'ah). This is understood as an illness that would make attending the prayer burdensome, similar to the difficulty of walking in rain or mud.

Therefore, if the missed Hajj or Umrah due to Iḥṣār (prevention) was either a voluntary act or a non-established obligation, there is no requirement to make up for it in either case.

In addition, if the missed obligation is established in the pilgrim’s debt, such as the Hajj of Islam after the first years of capability, it remains in their debt. As for if the missed Hajj or Umrah is due to reasons other than Iḥṣār, if it was an obligation, it remains in their debt as it was. If it was voluntary, they must make it up immediately, just as if it had been invalidated, and along with making it up, they must as well offer a sacrifice. And Allah The Almighty Knows Best.