Interpretation of why the Boy was killed Khidr explains about his second action:وَأَمَّا الْغُلَأمُ فَكَانَ أَبَوَاهُ مُوْمِنَيْنِ فَخَشِينَا أَن يُرْهِقَهُمَا طُغْيَانًا وَكُفْرًا"And as for the boy, his parents were believers, and we feared he would oppress them by rebellion and disbelief." Ibn Abbas narrated from Ubayy bin Ka`b that the Prophet said:الْغُلَمُ الَّذِي قَتَلَهُ الْخَضِرُ طُبِعَ يَوْمَ طُبِعَ كَافِرًاThe boy Al-Khidr killed was destined to be a disbeliever from the day he was created.It was recorded by Ibn Jarir from Ibn Abbas. He said:فَكَانَ أَبَوَاهُ مُوْمِنَيْنِ فَخَشِينَا أَن يُرْهِقَهُمَا طُغْيَانًا وَكُفْرًا (his parents were believers, and we feared he would oppress them by rebellion and disbelief).Their love for him might make them follow him in disbelief.Qatadah said,"His parents rejoiced when he was born and grieved for him when he was killed. If he had stayed alive, he would have been the cause of their doom. So let a man be content with the decree of Allah, for the decree of Allah for the believer, if he dislikes it, is better for him than if He were to decree something that he likes for him."An authentic Hadith says;لَاا يَقْضِي اللهُ لِلْمُوْمِنِ مِنْ قَضَاءٍ إِلاَّ كَانَ خَيْرًا لَهAllah does not decree anything for the believer except it is good for him.And Allah says:وَعَسَى أَن تَكْرَهُواْ شَيْيًا وَهُوَ خَيْرٌ لَّكُمْand it may be that you dislike a thing which is good for you. (2:216)فَأَرَدْنَا أَن يُبْدِلَهُمَا رَبُّهُمَا خَيْرًا مِّنْهُ زَكَاةً وَأَقْرَبَ رُحْمًا