Nafi' (may Allah have mercy on him) said that Ubaydullah bin Abdullah (may Allah have mercy on him) and Salim bin Abdullah (may Allah have mercy on him) informed him that they both spoke to Sayyiduna Abdullah bin Umar (may Allah be pleased with him) when the army came against Sayyiduna Ibn al-Zubayr (may Allah be pleased with him), before he was killed. They both said: It will not harm you if you do not perform Hajj this year, for we fear that something will be put between you and the House. Sayyiduna Abdullah bin Umar (may Allah be pleased with him) said: "We set out with the Messenger of Allah (peace and blessings be upon him), and the disbelievers of Quraysh blocked (the way to) the House, so the Messenger of Allah (peace and blessings be upon him) slaughtered his sacrifice and shaved his head. I call you to witness that I have made Umrah obligatory upon myself. If Allah wills, I will set off; if the way between me and the House is left open, I will perform tawaf, and if something comes between me and it, then I will do as the Messenger of Allah (peace and blessings be upon him) did, and I was with him (peace and blessings be upon him)." Then he entered ihram for Umrah at Dhu al-Hulayfah, travelled for a while and said: "The matter of these two (Hajj and Umrah) is one and the same; I call you to witness that I have made Hajj obligatory along with my Umrah." Then he did not exit ihram from either of them until he exited on the day of sacrifice, and he offered a sacrifice. He used to say: "Whoever combines Hajj and Umrah and enters ihram for both together does not exit ihram until he exits from both together on the day of sacrifice; he performs a single tawaf for both, and the sa'y between Safa and Marwah, on the day he enters Makkah."
(b) His words "on the day he enters Makkah, he returns to Safa and Marwah" mean, and Allah knows best, that a single sa'y between Safa and Marwah on the day he enters Makkah, after the tawaf of arrival (tawaf al-qudum), suffices him for both; then the second release from ihram is not attained except by the tawaf of the House on the day of sacrifice, and Allah knows best.
(c) In all the other narrations from Nafi', it is Abdullah bin Abdullah and Salim who spoke to him, and (the name) Abdullah is more correct.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الحج / 10080