Al-Kahf 74

فَٱنطَلَقَا حَتَّىٰٓ إِذَا لَقِيَا غُلَٰمًا فَقَتَلَهُۥ قَالَ أَقَتَلْتَ نَفْسًا زَكِيَّةًۢ بِغَيْرِ نَفْسٍ لَّقَدْ جِئْتَ شَيْـًٔا نُّكْرًا ﴿٧٤﴾

Faintalaqa hatta itha laqiya ghulaman faqatalahu qala aqatalta nafsan zakiyyatan bighayri nafsin laqad jita shayan nukran

Then they both proceeded, till they met a boy, he (Khidr) killed him. Musa (Moses) said: "Have you killed an innocent person who had killed none? Verily, you have committed a thing "Nukra" (a great Munkar - prohibited, evil, dreadful thing)!" The Noble Quran