4:82
أَفَلاَ يَتَدَبَّرُونَ الْقُرْآنَ وَلَوْ كَانَ مِنْ عِندِ غَيْرِ اللّهِ لَوَجَدُواْ فِيهِ اخْتِلاَفاً كَثِيراً
Do they not consider the Qur'an (with care)? Had it been from other Than Allah, they would surely have found therein Much discrepancy.
23:68
أَفَلَمْ يَدَّبَّرُوا الْقَوْلَ أَمْ جَاءهُم مَّا لَمْ يَأْتِ آبَاءهُمُ الْأَوَّلِينَ
Do they not ponder over the Word (of Allah), or has anything (new) come to them that did not come to their fathers of old?
38:29
كِتَابٌ أَنزَلْنَاهُ إِلَيْكَ مُبَارَكٌ لِّيَدَّبَّرُوا آيَاتِهِ وَلِيَتَذَكَّرَ أُوْلُوا الْأَلْبَابِ
(Here is) a Book which We have sent down unto thee, full of blessings, that they may mediate on its Signs, and that men of understanding may receive admonition.
47:24
أَفَلَا يَتَدَبَّرُونَ الْقُرْآنَ أَمْ عَلَى قُلُوبٍ أَقْفَالُهَا
Do they not then earnestly seek to understand the Qur'an, or are their hearts locked up by them?