Asalamo`Alaykum Wa Rahmatullahi Wa Barakaatuh,
It was narrated that Ibn ‘Umar (may Allaah be pleased with him) said: “The Messenger of Allaah (peace and blessings of Allaah be upon him) said: ‘Whoever reads Soorat al-Kahf on the day of Jumu’ah, a light will shine for him from beneath his feet to the clouds of the sky, which will shine for him on the Day of Resurrection, and he will be forgiven (his sins) between the two Fridays.’” Al-Mundhiri said, this was narrated by Abu Bakr ibn Mardawayh in his Tafseer, with an isnaad with which there was nothing wrong.
(al-Targheeb wa’l-Tarheeb, 1/298)