It is narrated from Sayyiduna Anas bin Malik (may Allah be pleased with him) that the Prophet (peace and blessings be upon him) said: "Seek the hour that is hoped for on Friday, between the Asr prayer and the setting of the sun, and it is of this length," meaning the length of a handful.
Hadith Referenceالمعجم الكبير للطبراني / باب الألف / 743