Abu Najeeh says that once someone asked Sayyiduna Ibn Umar (may Allah be pleased with them both) about fasting on the day of Arafah, so he replied: I performed Hajj with the Prophet (peace and blessings be upon him), but he did not fast on that day. I performed Hajj with Sayyiduna Abu Bakr, Sayyiduna Umar, and Sayyiduna Uthman (may Allah be pleased with them), but they also did not fast on that day. I neither fast on that day nor do I command or forbid it, so if you wish, you may fast, and if you do not wish, then do not fast.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 5420
Hadith Gradingحکم دارالسلام:حديث صحيح بطرقه وشواهده ، وهذا إسناد ضعيف ، لإبهام الرجل الراوي عن ابن عمر .