Ibn Umar was asked about fasting on the Day of Arafah. He said, "I performed the pilgrimage with the Prophet ﷺ and he did not fast it. I performed the pilgrimage with Abu Bakr and he did not fast it. I performed the pilgrimage with Umar and he did not fast it. I performed the pilgrimage with Uthman and he did not fast it. I do not fast it myself, nor do I command it, nor do I forbid it."Sufyan once said, "From the one who asked Ibn Umar."
حدثنا إسماعيل بن إبراهيم وسفيان بن عيينة قالا
سئل ابن عمر عن صوم يوم عرفة فقال حججت مع النبي ﷺ فلم يصمه وحججت مع أبي بكر فلم يصمه وحججت مع عمر فلم يصمه وحججت مع عثمان فلم يصمه وأنا لا أصومه ولا آمر به ولا أنهى عنه وقال سفيان مرة عمن سأل ابن عمر
Its isnad is sahih. Abu Najeeh is Yasar Thaqafi, whose reliability was established earlier at 603, and we add here that Bukhari gave him a biographical entry in al-Kabir 4/2/420. Tirmidhi said, Yasar Abu Najeeh Makki heard from Ibn Umar, and his son Abdullah bin Abu Najeeh narrated from him. Sufyan's narration of it on one occasion from someone who asked Ibn Umar does not undermine the connected narration. Tirmidhi related it at 2:56 from Ahmad bin Mani and Ali bin Hajar, from Sufyan bin Uyayna and Ismail bin Ibrahim, with this same isnad, and he said, The hadith is hasan. Abu Najeeh's name was Yasar, and he did hear from Ibn Umar.This hadith has also been narrated from Ibn Abu Najeeh, from his father, from a man, from Ibn Umar. Its commentator said, It appears that Abu Najeeh first heard this hadith through an intermediary, then later met Ibn Umar and heard it from him directly without any intermediary. The hadith has been attributed to Nasai and Ibn Hibban. See also what came earlier in the Musnad of Ibn Abbas at 3476 and 3477, along with the hadiths we referenced there, and what came earlier in the Musnad of Fadl bin Abbas at 1870.