Abdullah bin Rafi' narrates from Sayyiduna Abu Hurayrah (may Allah be pleased with him) that the Messenger of Allah (peace and blessings be upon him) said: "'The promised day' means the Day of Resurrection, 'the witness' means the day of Jumu'ah, and 'the witnessed' means the day of Arafah."
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الجمعة / 5564