The Letter Qaf - 50:2
"They thought it strange that a warner should come to them from among them! The disbelievers said, "This is a strange thing."
Allah sends His message in the language of the people and from among them so that it may be understood:
Prophet Joseph/12:2
We have sent it down as an Arabic Qur´an so that you may understand.
The Thunder/13:37
So We sent it down as an Arabic law. If you follow their pleasure after the knowledge that has come to you, you will have no friend or protector against Allah.
Prophet Abraham/14:4
We send every messenger only in the language of his people so that he may make them aware. Allah leads astray whom He wills and guides whom He wills. He is Mighty, Wise.
Mary/19:97
We have made it easy with your tongue, that you may give glad tidings with it to the righteous and warn the stubborn people.
Ta-Ha/20:113
So We have sent it down as a Qur´an in Arabic, and We have explained in it the news of the future in various forms so that they may act righteously or it may be a reminder for them.
The Poets/26:193
The Trustworthy Spirit (Gabriel) has sent it down.
The Poets/26:194
Into your heart... That you may be one of the warners.
The Poets/26:195
In a clear Arabic language.
The Poets/26:196
It has also been mentioned in the previous Books.
The Companies/39:27
We have given mankind every kind of example in this Qur´an so that they may take admonition.
The Companies/39:28
A smooth Quran in Arabic, may they be righteous
Explained in Detail/41:3
It is a Book whose verses are explained as an Arabic Qur´an for a people who know.
Explained in Detail/41:44
"Had We made it a Qur´an in a foreign language, they would have said, "Should not its verses have been explained?"Whether in a foreign language or in Arabic, say, "It is a guide and a cure for those who believe (regardless of their language). As for those who do not believe, their ears are heavy. It is closed to them as if it were addressed to them from a distant place."
The Ornaments of Gold/43:3
We have made it a Quran with a perfect language so that you may understand.
The Smoke/44:58
We have made it easy in your language that they may take admonition.
The Sandhills/46:12
Before that the Book of Moses was a guide and a mercy. This is a confirming Book sent down in Arabic to warn the wrongdoers and as good tidings to those who do good.
Prophet Jonah/10:16
"Say: "Had Allah not willed, I could not have recited it to you and you would not have known of it. I lived among you for a lifetime before that, do you not understand?"
The Family Of Imran/3:164
Allah was gracious in sending from among the believers a messenger who recited to them His Verses, purified them and taught them the Book and wisdom. But they were in manifest error before!