Translation of the verse 24 from Surah Muhammad : Number of verses 38 - - page 509 - Part 26.
Do they not then think deeply in the Quran, or are their hearts locked up (from understanding it)?
Then do they not reflect upon the Qur'an, or are there locks upon [their] hearts?
(47:24) Do they, then, not reflect on the Qur'an? Or are there locks on their hearts? *35
*35) That is, 'Either these people do not ponder over the Qur'an at all, or if they try to ponder over it, its teachings and meaning do not enter their hearts, because they have put locks on them." As for this that "there are their locks upon the hearts," it means this: "There are such locks on them as are specially meant for the hearts which are not susceptible to the truth."
Source : Muhammad Verse 24: Then do they not reflect upon the Qur'an, or are there locks upon [their] hearts?