Salim bin Abdullah bin Umar reported,
Abdul-Malik bin Marwan wrote to Hajjaj bin Yusuf instructing him not to differ from Abdullah bin Umar in anything concerning the rites of Hajj.On the Day of Arafah, when the sun had passed its zenith, Abdullah bin Umar came to Hajjaj, and I was with him. He called out at the entrance of Hajjaj's tent, "Where is this man?"Hajjaj came out to him wearing a saffron-dyed wrap and asked, "What is the matter, Abu Abdul-Rahman?"Abdullah said, "Time to set off, if you wish to follow the Sunnah."Hajjaj asked, "At this hour?"Abdullah replied, "Yes."Hajjaj said, "Give me a moment to pour some water over myself, then I will come out."So Abdullah dismounted and waited until Hajjaj came out. Hajjaj then walked between me and my father, and I said to him, "If you wish to follow the Sunnah today, then shorten the sermon and hasten the prayer."Hajjaj began looking toward Abdullah bin Umar to hear this confirmed by him. When Abdullah saw that, he said, "Salim has spoken the truth."
Azami 5090
Sahihعن سالم بن عبد الله أنه قال
كتب عبد الملك بن مروان إلى الحجاج بن يوسف: أن لا تخالف عبد الله بن عمر في شيء من أمر الحج. قال: فلما كان يوم عرفة، جاءه عبد الله بن عمر حين زالت الشمس وأنا معه، فصاح به عند سرادقه: أين هذا؟ فخرج عليه الحجاج وعليه ملحفة معصفرة، فقال: ما لك يا أبا عبد الرحمن؟ فقال: الرواح إن كنت تريد السنة. فقال: أهذه الساعة؟ قال: نعم. قال: فأنظرني حتى أفيض علي ماء، ثم أخرج، فنزل عبد الله، حتى خرج الحجاج فسار بيني وبين أبي، فقلت له: إن كنت تريد أن تصيب السنة اليوم فاقصر الخطبة وعجل الصلاة. قال: فجعل ينظر إلى عبد الله بن عمر كيما يسمع ذلك منه، فلما رأى ذلك عبد الله قال: صدق سالم.
Malik narrated it in the Book of Hajj (194) from Ibn Shihab, from Salim, with this wording. Bukhari narrated it in the Book of Hajj (1660) via the route of Malik, with the same, similarly. He also narrated it (1662) as a suspended report from Layth, "Aqeel narrated to me, from Ibn Shihab, who said, Salim informed me,'That Hajjaj bin Yusuf, the year he besieged Ibn Zubayr 
, asked Abdullah, "How do you act at the standing on the day of Arafah?" Salim said, "If you want the sunnah, then pray it early on the day of Arafah." Abdullah bin Umar said, "He has spoken truly, they used to combine Dhuhr and Asr in the sunnah." I said to Salim, "Did the Messenger of Allah ﷺ do that?" He said, "Do they follow in that anything but his sunnah?!"'"Ibn Hajar said in Fath al-Bari (3/514), "Ismaili connected it via the route of Yahya bin Bukayr and Abu Salih, both of them from Layth."As for what Saeed bin Hassan narrated, from Ibn Umar, who said, "When Hajjaj killed Ibn Zubayr, he sent to Ibn Umar, asking, 'At what hour did the Messenger of Allah ﷺ used to set out on this day?' He said, 'When that time came, we would set out.' Then when Ibn Umar wanted to set out, they said, 'It has not yet declined.' He said, 'Has the sun declined?' They said, 'The sun has not declined.' Then when they said, 'The sun has declined,' he set out." This chain contains Saeed bin Hassan, whom no one has affirmed as reliable, though Ibn Hibban mentioned him in Thiqat. Only two people narrated from him, so he is "acceptable" according to Ibn Hajar.Via his route, Abu Dawud narrated it (1914) from Ahmad, and it is in his Musnad (4782), and Ibn Majah also narrated it (3009) from Waki, who said, "Nafi bin Umar al-Jumahi narrated to us, from Saeed bin Hassan," and he related it.