Ihsar is an Arabic word which means being prevented from completing Hajj or ‘Umrah.
Ihsar means obstruction. It is the hindrances that the pilgrims may come across when he/she is on the way to perform Hajj or Umrah. It is a situation in which the pilgrim who is in a state of Ihram is obstructed to perform Hajj or Umrah. It takes place either because of reasons like illness, or shortage of money. However, a pilgrim should not hasten to make Tahallul, if it is hoped that the impediment will soon end.
Al-lhsar (as used in the Qur’an) means blocking the path to the House of Allah. Allah says, And complete the Hajj or `Umrah in the service of Allah. But if you are prevented (from completing it) send an offering for sacrifice. Quran Surah Al-Baqarah 2:196
A'isha (Allah be pleased with her) reported that Allah's Messenger (ﷺ) went (into the house of) Duba'a bint Zubair and said to her:Did you intend to perform Hajj? She said: By Allah, (I intend to do so) but I often remain ill, whereupon he (the Prophet) said to her: Perform Hajj but with con- dition, and say: “Allahumma mahilli Haisu Habastani” meaningO Allah, I shall be free from Ihram where you detain me. And she (Duba'a) was the wife of Miqdad.
So If a person reads the dua “Allahumma mahilli Haisu Habastani” (O Allah, I shall be free from Ihram where you detain me) (1), there is a great benefit, as, if he happens to face any hindrance and is stopped before reaching Makkah, then he can remove his Ihram where he was stopped and will not have to give Dum (Sacrificing a sheep).