Surah Kahf

Sūrat al-Kahf (Arabic: سورة الكهف‎, "The Cave") is the 18th surah of the Qur'an with 110 ayat. It is a Meccan sura.

As-hab al-Kahf

Verses 9 - 26[1] of the chapter tell the story of the As-hab al-Kahf (Arabic: أَصـحـاب الـكَـهـف‎, "People of the Cave"). A few young believers lived in a time when they were tortured for their beliefs. Upon the guidance of Allah, they fled the city, where believers were persecuted, together with their kalb (Arabic: كَـلـب‎, dog), and took refuge in a cave where they fell asleep. When they woke they found themselves that the people of the city had become believers.
The story of the rich and the poor

In verses 32 - 44 the surah discusses a parable of two men, one of whom had been given blessings from God and the other poor. The rich one wronged his soul and started showing off with his wealth and noble lineage.

And he had fruit, so he said to his companion while he was conversing with him, "I am greater than you in wealth and mightier in [numbers of] men."
-  Quran, Al-Kahf (The Cave), Ayah 34[2][3]

At the end of the parable God destroys what he had given the man.[4]
Moses and Al-Khidr
Main article: Islamic view of Moses

The third main story within the chapter (verses 60 - 82[5]) is that of Musa (Moses) traveling to gain knowledge from another servant of God who is never mentioned by name, in tafsir of ibn Kathir he is called Al-Khidr.[6]
Dhul-Qarnayn
Main article: Dhul-Qarnayn

Finally, the surah mentions in verses 83 - 98[7] a man who traveled a great deal and reached the east and the west of the earth - namely, Dhul-Qarnayn. The Qur'an repeats the Syrian legend of a great king who helps a tribe of people build a massive wall of iron between two mountains. It goes on to say that this wall will be only destroyed on Judgement Day[8] The wall may have reflected a distant knowledge of the Great Wall of China (the 12th century scholar al-Idrisi drew a map for Roger of Sicily showing the "Land of Gog and Magog" in Mongolia), or of various Sassanid Persian walls built in the Caspian area against the northern barbarians, or a conflation of the two.

Muslim historian and hagiographer Muhammad bin Ishaq reported in his book Sirah Rasul Allah that the eighteenth chapter of the Qur'an (which includes the story of Dhu l-Qarnayn) was revealed to the Islamic prophet Muhammad by Allah on account of some questions posed by rabbis residing in the city of Medina - the verse was revealed during the Meccan period of Muhammad's life. According to Ibn Ishaq, Muhammad's tribe, the powerful Quraysh, were greatly concerned about their tribesman who had started claiming prophethood and wished to consult rabbis about the matter. The Quraysh sent two men to the rabbis of Medina, reasoning that they had superior knowledge of the scriptures and about the prophets of God. The two Quraysh men described their tribesman, Muhammad, to the rabbis.

The rabbis told the men to ask Muhammad three questions:

They [the rabbis] said, "Ask him about three things which we will tell you to ask, and if he answers them then he is a Prophet who has been sent; if he does not, then he is saying things that are not true, in which case how you will deal with him will be up to you. Ask him about some young men in ancient times, what was their story for theirs is a strange and wondrous tale. Ask him about a man who travelled a great deal and reached the east and the west of the earth. What was his story and ask him about the Ruh (soul or spirit) - what is it? If he tells you about these things, then he is a Prophet, so follow him, but if he does not tell you, then he is a man who is making things up, so deal with him as you see fit."