Sūra al-Kahf (Arabic: سورة الكهف) is eighteenth sura of the Qur'an. It is a makki sura and located in juz's fifteen and sixteen. The word "kahf" means "cave". This sura is named "kahf" because it speaks about the story of the Companions of the Cave. Sura al-Kahf invites people to believe in the truth and do righteous deeds and emphasizes that God has no child.
Several stories are mentioned in this sura, three of which are more comprehensive than others: the story of the Companions of the Cave, the story of Prophet Moses (a) and one of God's servants (Khidr (a)) and the story of Dhu l-Qarnayn. It is said that sura al-Kahf was revealed when some people from Quraysh were supposed to learn from Jews some issues and test the Prophet (s) with them. Those issues were questions from the three mentioned stories and also the time of the Day of Judgement.
One of the famous verses of Sura al-Kahf is verse fifty which refers to the story of angel's prostration to Adam (a) and disobedience of Satan. There are many narrations about the merits of recitation of Sura al-Kahf, including a hadith narrated from the Prophet (s) that upon the revelation of Sura al-Kahf, seventy thousand angels followed it and its glory filled the skies and the earth; whoever recites it on Friday, God will forgive his sins until the next Friday and will give him a light which shines up to the sky and he will be safe from the trial of Dajjal.