Do they not then think deeply in the Qur'an, or are their hearts locked up (from understanding it)?

قُلِ ادْعُوا الَّذِينَ زَعَمْتُمْ مِنْ دُونِهِ فَلاَ يَمْلِكُونَ كَشْفَ الضُّرِّ عَنكُمْ وَلاَ تَحْوِيلاً
الإسراء: 56
أُوْلَئِكَ الَّذِينَ يَدْعُونَ يَبْتَغُونَ إِلَى رَبِّهِمُ الْوَسِيلَةَ أَيُّهُمْ أَقْرَبُ وَيَرْجُونَ رَحْمَتَهُ وَيَخَافُونَ عَذَابَهُ إِنَّ عَذَابَ رَبِّكَ كَانَ مَحْذُورًا
 الإسراء: 57



56. Say (O Muhammad ): "Call unto those besides Him whom you pretend [to be gods like angels, Iesa (Jesus), 'Uzair (Ezra),angels,auliya etc.]. They have neither the power to remove the adversity from you nor even to shift it from you to another person."
57. Those whom they call upon ,desire (for themselves) means of access to their Lord (Allah), as to which of them should be the nearest and they hope for His Mercy and fear His Torment. Verily, the Torment of your Lord is something to be afraid of!