Sayyiduna Ibn Abbas (may Allah be pleased with them both) narrated from the Messenger of Allah (peace and blessings be upon him), he (peace be upon him) said: "This is the ‘Umrah from which we have benefited, so whoever does not have a sacrificial animal should come out of ihram." It was asked to him, what kind of coming out of ihram is meant? (i.e., from which restrictions of ihram is one exempted?) He (peace be upon him) said: "All matters (which were forbidden due to ihram) have become permissible." He said: "‘Umrah has been included in Hajj until the Day of Resurrection." Ishaq (may Allah have mercy on him) said: That is, performing ‘Umrah in the months of Hajj is permissible until the Day of Resurrection, and this is because the people of the Age of Ignorance did not consider it permissible to perform ‘Umrah in the months of Hajj.
Hadith Referenceمسند اسحاق بن راهويه / كتاب المناسك / 358
Hadith Takhrij«مسلم ، كتاب الحج ، باب جواز العمرة فى اشهر الحج ، رقم : 1241 . سنن ابوداود ، رقم : 1790 . سنن نسائي ، رقم : 2815 . سنن ابن ماجه ، رقم : 2977»
Sayyiduna Ibn Abbas (may Allah be pleased with them both) said: The Messenger of Allah (peace and blessings be upon him) and his companions came to perform Hajj, so the Messenger of Allah (peace and blessings be upon him) said: "O people! End your state of Ihram, except for the one who has a sacrificial animal with him. If I had known what I know now, I would not have done this. Umrah has been incorporated into Hajj until the Day of Resurrection."
Hadith Referenceمسند اسحاق بن راهويه / كتاب المناسك / 359