Tafseer Ibn Kathir of AR RA'D [1]

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

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

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

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

  (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.