18:74
فَٱنطَلَقَا حَتَّىٰٓ إِذَا لَقِيَا غُلَـٰمًا فَقَتَلَهُۥ قَالَ أَقَتَلْتَ نَفْسًا زَكِيَّةًۢ بِغَيْرِ نَفْسٍ لَّقَدْ جِئْتَ شَيْـًٔا نُّكْرًا
fa-inṭalaqā ḥattā idhā laqiyā ghulāman faqatalahu qāla aqatalta nafsan zakiyyatan bighayri nafsin laqad ji'ta shayan nuk'ran
And so they travelled on. Then, when they met a young boy and the man killed him, Moses said, ‘How could you kill an innocent person? He has not killed anyone! What a terrible thing to do!’
Then they both proceeded, till they met a boy, and he (Khidr) killed him. Mûsâ (Moses) said: "Have you killed an innocent person who had killed none? Verily, you have committed a thing Nukr (a great Munkar - prohibited, evil, dreadful thing)!"