Ar-Ra'd 13:1

Ar-Rad was revealed in Makkah

بِسْمِ اللَّهِ الرَّحْمَـنِ الرَّحِيمِ

In the Name of Allah, the Most Gracious, the Most Merciful

The Qur'an is Allah's Kalam (Speech)

We talked before, in the beginning of Surat Al-Baqarah (chapter 2) about the meaning of the letters that appear in the beginnings of some chapters in the Qur'an. We stated that every Surah that starts with separate letters, affirms that the Qur'an is miraculous and is an evidence that it is a revelation from Allah, and that there is no doubt or denying in this fact. This is why Allah said next,

تِلْكَ آيَـتُ الْكِتَـبِ

(These are the verses of the Book), the Qur'an, which Allah described afterwards,

وَالَّذِى أُنزِلَ إِلَيْكَ

(and that which has been revealed unto you), O Muhammad,

مِن رَبِّكَ الْحَقُّ

(from your Lord is the truth,) Allah said next,

وَلَـكِنَّ أَكْثَرَ النَّاسِ لاَ يُؤْمِنُونَ

(but most men believe not.) just as He said in another Ayah,

وَمَآ أَكْثَرُ النَّاسِ وَلَوْ حَرَصْتَ بِمُؤْمِنِينَ

(And most of mankind will not believe even if you desire it eagerly.) 12:103 Allah declares that even after this clear, plain and unequivocal explanation (the Qur'an), most men will still not believe, due to their rebellion, stubbornness and hypocrisy.

اللَّهُ الَّذِى رَفَعَ السَّمَـوَتِ بِغَيْرِ عَمَدٍ تَرَوْنَهَا ثُمَّ اسْتَوَى عَلَى الْعَرْشِ وَسَخَّرَ الشَّمْسَ وَالْقَمَرَ كُلٌّ يَجْرِى لأَجَلٍ مُّسَمًّـى يُدَبَّرُ الاٌّمْرَ يُفَصِّلُ الآيَـتِ لَعَلَّكُمْ بِلِقَآءِ رَبِّكُمْ تُوقِنُونَ

Tafsir Ibn Kathir (abridged, English).