Surah Al-Isra
۞ وَقَضَىٰ رَبُّكَ أَلَّا تَعْبُدُوٓا۟ إِلَّآ إِيَّاهُ وَبِٱلْوَٰلِدَيْنِ إِحْسَـٰنًا ۚ إِمَّا يَبْلُغَنَّ عِندَكَ ٱلْكِبَرَ أَحَدُهُمَآ أَوْ كِلَاهُمَا فَلَا تَقُل لَّهُمَآ أُفٍّ وَلَا تَنْهَرْهُمَا وَقُل لَّهُمَا قَوْلًا كَرِيمًا
Wa qaḍā rabbuka allā ta‘budū illā iyyāhu wa bil-wālidaini iḥsānā(n), immā yabluganna ‘indakal-kibara aḥaduhumā au kilāhumā falā taqul lahumā uffiw wa lā tanhar humā wa qul lahumā qaulan karīmā(n).
And your Lord has decreed that you not worship except Him, and to parents, good treatment. Whether one or both of them reach old age [while] with you, say not to them [so much as], "uff," and do not repel them but speak to them a noble word.
📝 Footnotes
426) Merely saying a disrespectful word like "uff" (or any other harsh words) to parents is forbidden in religion, let alone treating them with greater harshness.