Translation:

59. Thus does Allah seal up the hearts of those who understand not.

Notes (Tafseer)

3577. When an attitude of obstinate resistance to Truth is adopted, the natural consequence (by Allah's Law) is that the heart and mind get more and more hardened with every act of deliberate rejection. It becomes more and more impervious to the reception of Truth, just as a sealed envelope is unable to receive any further letter or message after it is sealed. Cf. also ii. 7 and n. 31.