We place shields over their hearts, that they should not understand it, and deafness in their ears. If you mention your Lord in the Quran alone, they run away turning their backs in aversion.
Translation endnotes
[17:46] Those who do not acknowledge the hereafter with certainty will not understand the Quran, and they will claim that the Quran is difficult or even impossible to understand on its own. See 54:17,22,32,and 40. Traditional translations and commentaries somehow separate the word “Quran” from the adjective (wahdahu = alone, only) that follows it. They translate it as "Lord alone in the Quran." Though there are many verses emphasizing God's oneness (see 39:45), this verse could be understood as another one emphasizing that message. However, this could be only a secondary meaning of this particular verse, since the adjective wahdehu is used not after the word Rab (Lord) but after the word Quran. In Arabic if one wants to say ‘Quran alone,’ the only way of saying it is "Quranun wahdahu." The mathematical structure of the Quran too confirms our translation. For instance, the word wahdahu is used for God in 7:70; 39:45; 40:12,84 and 60:4. If we add these numbers we get 361, or 19x19. However, if we add 17:46, where the word wahdahu is used for the Quran, the total is not in harmony with the great mathematical system.