Surah Al-Kahf
فَٱنطَلَقَا حَتَّىٰٓ إِذَا لَقِيَا غُلَٰمًۭا فَقَتَلَهُۥ قَالَ أَقَتَلْتَ نَفْسًۭا زَكِيَّةًۢ بِغَيْرِ نَفْسٍۢ لَّقَدْ جِئْتَ شَيْـًۭٔا نُّكْرًۭا
“So they set out, until when they met a boy, al-Khidh r killed him. [Moses] said, "Have you killed a pure soul for other than [having killed] a soul? You have certainly done a deplorable thing."”
Translation: Saheeh International
Reflection — Ibn Kathir
The Story of killing the Boy
فَانطَلَقَا
(Then they both proceeded,) means, after the first incident,
Reflection — Maarif ul Quran
We now move to the sentence: حَتَّىٰ إِذَا لَقِيَا غُلَامًا (until when they met a boy -74). The word: غُلَام (ghulam) in the text is used for a minor boy in the Arabic usage. This boy killed by al-Khadir (علیہ السلام) was a minor - as corroborated by Sayyidna Ibn ` Abbas ؓ and most commentators. Further on, when the words: نَفْسًا زَكِيَّةً (innocent person) were used for him, that too supports the view that he was a minor. The reason is that زَكِيَّةً (zakiyyah) means 'free of sin' and it can be either the attribute of a prophet or a minor child who faces no accounting for what is done by him and no sin is written in his Book of Deeds.
What does this verse bring up for you today?