وَأَمَّا ٱلۡغُلَٰمُ فَكَانَ أَبَوَاهُ مُؤۡمِنَيۡنِ فَخَشِينَآ أَن يُرۡهِقَهُمَا طُغۡيَٰنٗا وَكُفۡرٗا ٨٠
And as for the boy, his parents were believers, and we feared that he would overburden them by transgression and disbelief.
Translation: Saheeh International (English)
Each word's meaning and sound
As for the boy you criticised me for killing, his parents were believers but he was an unbeliever according to Allah’s knowledge. So I feared that if he grew up, he would cause them to disbelieve in Allah out of their intense love for him or their intense need towards him.
Al-Mukhtasar in interpreting the Noble Quran