وَلَوْ جَعَلْنَاهُ قُرْآنًا أَعْجَمِيًّا لَّقَالُوا لَوْلَا فُصِّلَتْ آيَاتُهُ ۖ أَأَعْجَمِيٌّ وَعَرَبِيٌّ ۗ قُلْ هُوَ لِلَّذِينَ آمَنُوا هُدًى وَشِفَاءٌ ۖ وَالَّذِينَ لَا يُؤْمِنُونَ فِي آذَانِهِمْ وَقْرٌ وَهُوَ عَلَيْهِمْ عَمًى ۚ أُولَـٰئِكَ يُنَادَوْنَ مِن مَّكَانٍ بَعِيدٍ ﴿٤٤﴾

Wa law ja'alnaahu Qur-aanan a'jamiyyal-laqaaloo lawlaa fussilat aayaatuhoo 'a-a'jamiyyun wa 'Arabiyy; qul huwa lillazeena aamanoo hudan wa shifaaa'; wallazeena laa yu'minoona feee aazaanihim waqrun wa huwa 'alaihim 'amaa; ulaaa'ika yunaadawna mim-makaanim-ba'eed.

(44) And if We had made it a non-Arabic Qur'an, they would have said, "Why are its verses not explained in detail [in our language]? Is it a foreign [recitation] and an Arab [messenger]?" Say, "It is, for those who believe, a guidance and cure." And those who do not believe - in their ears is deafness, and it is upon them blindness. Those are being called from a distant place.

Reference: Surah Fussilat 41:44