Tafsir of Al-Kahf 18:74

{فقتله} (Then he killed him): It is said: He killed him by twisting his neck. It is also said: He struck his head against a wall. From Sa‘id ibn Jubayr: He laid him down and slaughtered him with a knife.

If you ask: Why is it said, “Until, when they boarded the ship, he scuttled it” (without a fa), while it is said, “Until, when they met a boy, he killed him” (with a fa)?

I say: In the first, the scuttling is made the consequence (jaza’) of the condition (shart). In the second, the killing is made part of the condition itself, conjoined to it, while the consequence is his saying, “Have you killed...?”

If you ask: Why the difference between them?

I say: Because the scuttling of the ship did not immediately follow the boarding, whereas the killing did immediately follow the meeting of the boy.

{زاكية} (Pure/Innocent): It is read as zakiyah and zakiyyah. It means pure from sins, either because she was pure in his sight—as he did not see her commit a sin—or because she was a child who had not yet reached the age of accountability.

{بغير نفس} (Without [having killed] a soul): Meaning, he did not kill a soul for which he should be executed in retaliation.

From Ibn ‘Abbas: Najdah al-Haruri wrote to him: "How was his killing permissible, when the Messenger of Allah (ﷺ) forbade the killing of children?" He wrote back: "If you know of the state of children what the scholar of Musa knew, then you may kill."

{نكرا} (A grievous thing): It is read with two dammahs (nukuran), meaning something rejected/abhorrent. It is said that nukr is less severe than imr (the "grave matter" mentioned earlier), because killing one soul is lighter than drowning the people of the ship. It is also said: It means, "You have committed something more rejected than the first," because the first was a hole that could be remedied by patching, whereas this has no way to be remedied.

If you ask: What is the meaning of the addition of “laka” (to you) in “qad balaghta min ladunni ‘udhura” (you have received from me an excuse)?

I say: It is an addition to emphasize the confrontation through rebuke for abandoning the instruction, and to mark his lack of patience upon the second occurrence.

{قال إن سألتك عن شىء بعدها فلا تصاحبنى قد بلغت من لدنى عذرا} (He said, "If I ask you about anything after this, then do not keep me as a companion. You have received from me an excuse.")