Sahih Bukhari Volume 2, Book 13, Hadith Number 57

Narated By Abu Huraira : Allah’s Apostle (p.b.u.h) talked about Friday and said, “There is an hour (opportune time) on Friday and if a Muslim gets it while praying and asks something from Allah, then Allah will definitely meet his demand.” And he (the Prophet) pointed out the shortness of that time with his hands.