Why the Qu'ran is in Arabic

وَلَوۡ جَعَلۡنَـٰهُ قُرۡءَانًا أَعۡجَمِيًّ۬ا لَّقَالُواْ لَوۡلَا فُصِّلَتۡ ءَايَـٰتُهُ ۥۤ‌ۖ ءَا۠عۡجَمِىٌّ۬ وَعَرَبِىٌّ۬‌ۗ قُلۡ هُوَ لِلَّذِينَ ءَامَنُواْ هُدً۬ى وَشِفَآءٌ۬‌ۖ وَٱلَّذِينَ لَا يُؤۡمِنُونَ فِىٓ ءَاذَانِهِمۡ وَقۡرٌ۬ وَهُوَ عَلَيۡهِمۡ عَمًى‌ۚ أُوْلَـٰٓٮِٕكَ يُنَادَوۡنَ مِن مَّكَانِۭ بَعِيدٍ۬

Had We sent this as a Qur'an (in a language) other than Arabic, they would have said: "Why are not its verses explained in detail? What! (a Book) not in Arabic and (a Messenger) an Arab?"

Say: "It is a guide and a healing to those who believe; and for those who believe not there is a deafness in their ears, and it is blindness in their (eyes); they are (as it were) being called from a place far distant!"

(Qur'an 41:44)