Abu Huraira reported God’s Messenger as saying, "The promised day is the day of resurrection, the day which is witnessed is the day of ‘Arafa, and the witness* is Friday on no more excellent day than which has the sun risen or set. It contains a time at which no believing worshipper will supplicate God for what is good without God answering him, or seek refuge from something without His giving him refuge from it.”
* Al-Qur’an; 85:2 f.
Ahmad and Tirmidhi transmitted it, the latter saying that this is a gharib tradition known only among the traditions of Musa b. ‘Ubaida who is declared to be weak.