It is narrated from Hazrat Abu Huraira (may Allah be pleased with him), either as a mawquf or marfu' narration, that in "washaahid wa mashhood," the "shaahid" refers to the Day of Arafah and the "mashhood" refers to the Day of Resurrection.
Hadith Referenceمسند احمد / مسند المكثرين من الصحابة / 7973