[...hearts by which to reason, or ears by which to hear?] Meaning: Had they traveled and reflected, they would have been warned by what befell their brethren among the disbelievers, and they would have repented had they possessed hearts by which to reason. [For indeed, it is not eyes that are blinded, but blinded are the hearts which are within the breasts.] Meaning: They were only ruined because of their hearts.

Surah Al-Hajj from (verse 47 to verse 51).