Tawoos says that the Messenger of Allah ﷺ left Madinah, but he ﷺ did not mention Hajj or Umrah; rather, he was waiting for revelation. When he ﷺ was between Safa and Marwah, revelation came down at that time. So he ﷺ ordered those companions who had put on the Ihram (for Hajj) and did not have a sacrificial animal with them to make it Umrah instead. And the Messenger of Allah ﷺ said: "If I had known earlier what I came to know later, I would not have brought the sacrificial animal. But I have stuck my hair (i.e., completed the rites) and brought the sacrificial animal, so now I cannot come out of Ihram without offering the sacrifice."
Suraqah bin Malik (may Allah be pleased with him) stood up towards you ﷺ and said: "O Messenger of Allah! Decide for us as if we are a people who have just been born. Is this Umrah only for this year or forever?" You ﷺ said: "Rather, it is forever. Now Umrah during the (days of) Hajj has been included until the Day of Resurrection."
Tawoos said: (In Makkah) Ali (may Allah be pleased with him) arrived from Yemen, so the Prophet ﷺ asked him: "With what intention did you put on Ihram?" One of Maysarah or Hisham bin Hujairah narrated from Tawoos that Ali (may Allah be pleased with him) said: "With the Ihram of the Prophet ﷺ (i.e., with the same intention as you ﷺ did)," and the other said: "I am present with the Hajj of the Prophet ﷺ."
Hadith Referenceمسند الإمام الشافعي / كتاب الحج / 803
Hadith Takhrijاسناده ضعيف لإرساله اخرجه البيهقي : 6/5 ۔ وفى المعرفة السنن والآثار له (2683)۔