Fiqh-us-Sunnah Volume 5, Hajj and ‘Umrah, Fiqh 5.130A.
Commenting on the Qur’anic verse “But if you are prevented (from completing it) send an offering for sacrifice,” Ibn ‘Abbas said, “If one intended to perform either Hajj or ‘Umrah, but was prevented from approaching the House of Allah, then he must slaughter whatever animal he can afford, a sheep or a larger animal.”
If a person intended to perform the obligatory Hajj (and he was prevented), he must make it up later, but if he was intending a supererogatory Hajj, he does not have to make up for it.
Malik said that he was told that the Prophet (peace be upon him) and his Companions came to Hudaibiah, and there they slaughtered their animals, shaved their heads, terminated their ihram, and resumed their normal course of life, without having first made Tawaf of Ka’bah or without the sacrificial animals reaching the Ka’bah.
Likewise there is no record, according to Bukhari, that the Prophet (peace be upon him) ordered his Companions to make up for their (missed) ‘Umrah or return to the Sacred Mosque to repeat it, although Hudaibiah is outside the Sacred Precincts of Haram.
Ash-Shafi’i holds that a prevented person may slaughter his sacrificial animal at the place he is stopped and terminate his ihram and resume his normal life. He is not required to make up for what he missed, because Allah has not mentioned any such thing.
Ash-Shafi’i adds, “For we know from the recorded reports that some of the people who were with the Prophet (peace be upon him) at the time of Hudaibiah did not return the next year to make up for their missed ‘Umrah.
They were not forced to stay back for any excuse, sickness or worldly business. If making up for the ‘Umrah were essential the Prophet (peace be upon him) would have certainly commanded them to join him and not to stay back.”
Continuing, he further says, “This ‘Umrah was called the “‘Umrah tul Qada (or ‘Umrah performed in order to make up for the missed ‘Umrah)” because of the the dispute between the Prophet (peace be upon him) and the Quraish, and not because it was essential (wajib) and had to be made up later by another ‘Umrah.”