It was narrated from Nafi that

Ibn 'Umar wanted to perform Hajj in the year when Al-Hajjaj was besieging Ibn Az-Zubair, and it was said to him: "It seems that there will be fighting between them, and I am afraid that you will prevented from performing Hajj." He said: "In the Messenger of Allah you have a good example. I am going to do what the Messenger of Allah (ﷺ) did. I bear witness to you that I have resolved to perform 'Umrah." Then he set out, and when he was in Zahir Al-Baida, he said: "Hajj and Umrah are the same thing; I bear witness to you that I have resolved to perform Hajj with my 'Umrah." And he brought along a Hadi (sacrificial animal) that he had bought in Qudaid. Then he set out and entered Ihram for them both. When he came to Makkah he circumambulated the House and (did sa'i) between As-Safa and Al-Marwah. Then he did not do any thing more than that, and he did not offer a sacrifice, or shave his head, or cut his hair; he remained in Ihram until the Day of Sacrifice. Then he slaughtered his Hadi and shaved his head, and he thought that he had completed the Tawaf of Hajj and 'Umrah in the first Tawaf. Ibn 'Umar said: "That is what the Messenger of Allah (ﷺ) did.