Abdullah bin Umar reported,

When he set out for Mecca to perform Umrah during the time of the civil strife, he said, "If I am prevented from reaching the House, we will do as we did with the Messenger of Allah ﷺ." So he entered the state of ihram for Umrah, because the Messenger of Allah ﷺ had entered ihram for Umrah in the year of Hudaybiyyah.Then Abdullah reconsidered his situation and said, "The matter of the two is one and the same." He turned to his companions and said, "The matter of the two is one and the same. I call you to witness that I have made the Hajj obligatory upon myself along with the Umrah."Then he proceeded until he reached the House, where he made a single circumambulation, considering that sufficient for him, and he offered a sacrificial animal.

Azami 4955

Sahih

عن عبد الله بن عمر

أنه قال حين خرج إلى مكة معتمرا الفتنة: إن صددت عن البيت صنعنا كما صنعنا مع رسول الله ﷺ فأهل بعمرة من أجل أن رسول الله ﷺ أهل بعمرة عام الحديبية، ثم إن عبد الله نظر في أمره فقال: ما أمرهما إلا واحد، ثم التفت إلى أصحابه فقال ما أمرهما إلا واحد أشهدكم أني قد أوجبت الحج مع العمرة، ثم نفذ حتى جاء البيت فطاف طوافا واحدا ورأى ذلك مجزيا عنه وأهدى.

الأعظمي 4955صحيح
Contents
Reference
Commentary
Ayat
Collection
Jami al-Kamil
Book
Hajj
Chapter
Description of the Hajj of the Prophet ﷺ as narrated by Jabir and others, and the rulings mentioned therein
Section
Whoever changed his intention from tamattu to qiran before beginning tawaf
Numbering
Jami al-Kamil 4955 (2nd edition)
Azami 4955