The evidence for it being recommended includes the hadith related by Hakim and Bayhaqi, from Abu Sa`id (Allah be pleased with him), �Whoever recites Surat al-Kahf on Friday, light shall shine forth for him between the two Fridays.� [Ibn Hajar, Talkhis al-Habir]
It is mentioned in Heavenly Ornaments, by Imam al-Tahanawi: