Do they not reflect upon the Qur'an and examine what is in it of admonitions and warnings and threats to the sinners, so that they do not dare to commit sins? Then he said: Or are there locks upon their hearts? And 'or' here means 'but' and is an interrogative particle, to record against them that their hearts are locked and cannot be reached by remembrance. And from Qatadah: By Allah, they would find in the Qur'an a deterrent from disobeying Allah if they reflected upon it, but they have taken the ambiguous verses and thus perished. If you say: Why is 'hearts' indefinite while 'locks' is added to it? I say: As for the indefiniteness, there are two interpretations: that it refers to hard hearts whose condition is ambiguous in this regard. Or it refers to some hearts, namely the hearts of the hypocrites. And as for the addition of 'locks', it is because it refers to the locks specific to them, which are the locks of disbelief that have closed tightly and cannot be opened. And it has been recited: 'their locking', as a verbal noun.