Tafsir of Al-Kahf 18:109

Al-Midād (The Ink): The name for that with which an inkwell is supplied, such as ink, or that with which a lamp is supplied, such as oil. It is also said: "Fertilizer is the midād (sustenance) of the earth."

The Meaning: If the words of God’s knowledge and wisdom were to be written, and the sea were to serve as ink for them—and by "the sea," the genus is intended—the sea would be exhausted before the words were exhausted. Even if We brought another sea like it as ink, it too would be exhausted, while the words would remain inexhaustible.

• "Midādan" (as ink): This is a tamyīz (specifier), similar to your saying, "I have the like of him as a man."
• "Madad": This is synonymous with midād, meaning that which provides supply.
• Ibn Abbas (may Allah be pleased with him): Narrated as "bi-mithlihi midādan" (with the like of it as ink).
• Al-A‘raj: Recited it as midadan (with a kasra on the mīm), the plural of midda, which is that which a writer draws upon to write.
• Variant Reading: Yanfadu (with a yā’).

The Occasion of Revelation: It is said that Huyayy ibn Akhtab said: "In your Book, it says: 'And whoever is given wisdom has certainly been given much good' (Al-Baqarah: 269), yet you also read: 'And you have not been given of knowledge except a little' (Al-Isra: 85)." Thus, this verse was revealed, meaning: That [wisdom] is indeed much good, but it is merely a drop in the ocean of God’s words.

{ Say, "I am only a man like you, to whom has been revealed that your god is one God. So whoever would hope for the meeting with his Lord - let him do righteous work and not associate in the worship of his Lord anyone." }