Surah 18. Al-Kahf, Ayah 80

Lit., "we feared" - but it should be borne in mind that, beyond this primary meaning, the verb khashiya sometimes denotes "he had reason to fear" and, consequently, "he knew", i.e., that something bad would happen (Taj al-'Arus, with specific reference to the above verse): and so we may assume that the sage's expression of "fear" was synonymous with positive "knowledge" gained through outward evidence or through mystic insight (the latter being more probable, as indicated by his statement in the second paragraph of the next verse, "I did not do [any of] this of my own accord").

 This is the royal ‘we’.

This seemed at first sight even a more cruel act than scuttling the boat. But the danger was also greater. Khidhr knew that the youth was a potential parricide. His parents were worthy, pious people, who had brought him up with love. He had apparently gone wrong. Perhaps he had already been guilty of murders and robberies and had escaped the law by subtleties and fraud. See next note.