Abdullah bin Zubayr reported,
He was saying to Ubayd bin Umayr bin Qatada al-Laythi, "Tell us, Ubayd, how did the prophethood first begin for the Messenger of Allah ﷺ when Jibreel 
came to him?"Ubayd said, while I was present as he was narrating to Abdullah bin Zubayr and the people gathered around him, "The Messenger of Allah ﷺ used to retreat in seclusion at Hira for one month each year. This was a practice of devotional retreat that Quraysh observed in the days of ignorance, and tahannuth means seeking righteousness."Ubayd continued, "The Messenger of Allah ﷺ would spend that month in seclusion every year, honoring any poor people who came to him. When the Messenger of Allah ﷺ completed his seclusion for that month, the first thing he would do upon leaving his retreat, before entering his house, was to go to the Kaabah. He would circle it seven times, or as many times as Allah willed, and then return to his home."
Azami 8548
Hasanعن عبد الله بن الزبير
وهو يقول لعبيد بن عمير بن قتادة الليثي: حدثنا يا عبيد، كيف كان بدء ما ابتدئ به رسول الله ﷺ من النبوة، حين جاءه جبريل عليه السلام؟ قال: فقال: عبيد- وأنا حاضر يحدث عبد الله بن الزبير ومن عنده من الناس:- كان رسول الله ﷺ يجاور في حراء من كل سنة شهرا، وكان ذلك مما تحنث به قريش في الجاهلية، والتحنث التبرر. وقال عبيد: فكان رسول الله ﷺ يجاور ذلك الشهر من كل سنة، يعظم من جاءه من المساكين، فإذا قضى رسول الله ﷺ جواره من شهره ذلك كان أول ما بدأ به إذا انصرف من جواره الكعبة قبل أن يدخل بيته. فيطوف بها سبعا أو ما شاء الله من ذلك. ثم يرجع إلى بيته.
No references are available.
Ibn Ishaq narrated it, as found in Sirat bin Hisham (1/235). He said, Wahb bin Kaysan, the freedman of the family of Zubayr, told me, I heard Abdullah bin Zubayr saying to Ubayd bin Umayr bin Qatada al-Laythi, and then he mentioned it.Ubaydullah bin Umayr was among the senior Tabiin, and it is said he was born during the time of the Prophet ﷺ. Its chain is hasan because of Muhammad bin Ishaq.Before the revelation came down to him, the Prophet ﷺ followed the religion of Ibrahim, not worshipping idols and not eating what had been slaughtered for other than Allah. Whoever claims that he followed the religion of Isa , on the grounds that Isa was the last of the prophets of Banu Israil and that no prophet came between him and the Prophet ﷺ, has erred, because Isa came to renew the religion of Musa , which was exclusively for Banu Israil. It has indeed been established that Zayd bin Amr bin Nufayl followed the religion of Ibrahim before the Prophet ﷺ was sent as a prophet.