Short Answer
Most scholars said it is virtuous to recite Surat ul-Kahf (chapter 18) on Friday. Friday begins on Thursday night after sunset and lasts until Friday before sunset, so it can be recited during that time period. Since the effort and function of someone who recites is different than one who listens, it probably doesn’t reap the same reward, but there is virtue in listening to the Qur’an so if someone is unable to recite it, then hopefully they will get a similar reward for listening to it.
Reason for Asking the Question
Hadiths about the virtues of reciting this surah are often shared by people who want to earn the reward and know the details about that.
What the Prophet Said
“Whoever recites Surat ul-Kahf on Friday, Allah will give him a light that will shine between those two Fridays.” [Al-Bayhaqi 3:249, al-Hakim 2:399 #3392] [Ibn Hajar said in Takhrij ul-Adhkar that it is hasan and said that this is the strongest report about reciting Surat ul-Kahf; graded by Al-Albani as sahih in Sahih ul-Jami’]
Ibn Umar said: “The Messenger of Allah said: ‘Whoever reads Surat ul-Kahf on Friday will have a light that 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.’” [at-Targhib wa t-Tarhib 1:298] [al-Mundhiri said that this is a chain which has nothing wrong with it]
Abu Sa’id al-Khudri said: “Whoever reads Surat ul-Kahf on the night of Friday will have a light that will stretch between him and the Ancient House (the Ka’bah).” [ad-Darimi, #3407] . [graded by Al-Albani as sahih in Sahih ul-Jami’] [This is not a hadith of the Prophet but a statement of the Companion]
What the Scholars Said
Al-Munawi (d. 1031 AH): “It is recommended to read it during the day or night of Friday…Ibn Hajar said in al-Amali: ‘In some reports it says the day of Friday and in some reports it says the night of Friday. They (the reports) may be reconciled by saying that what is meant is the day which includes the night and vice versa.” [Fayd ul-Qadir Sharh Jami’ us-Saghir 6:198-199)
The narrations about reciting Surat ul-Kahf on Friday are slightly weak, though scholars who are lenient in grading like al-Hakim, al-Mundhiri, as-Suyuti, and al-Albani graded them authentic, while adh-Dhahabi, Ibn Kathir, and Ibn ul-Qayyim said the report is more likely to be attributed to Abu Sa’id al-Khudri or Ibn Umar rather than the Prophet. Nonetheless, scholars said it can be acted on. However, the very weak or fabricated narrations should never be relied upon or shared as encouragement.