That is because they believed, and then they disbelieved; so their hearts (63:3)

Almuntakhab Fi Tafsir Alquran Alkarim

They adopted the faith and then they dropped it -Simpletons- their hearts ears are closed and their breasts are filled with irreverence imposed upon their hearts by the evil hand

Tafseer Tafheem-ul-Quran by Syed Abu-al-A'la Maududi

(63:3) All that is because they first believed and then disbelieved, and therefore a seal was set on their hearts; as a result they understand nothing. *4

That is because they believed, and then they disbelieved; so their hearts meaning

*4) In this verse "believing" means professing the faith in order to be counted among Muslims, and 'disbelieving" means not to believe sincerely and to persist in disbelief as usual. The verse means to say that when they, after due thought, decided to adopt this hypocritical attitude instead of adopting either belief or disbelief plainly, Allah caused a seal to be set on their hearts and deprived them of the grace to adopt the attitude and conduct of a true, sincere and noble person. Now, their power of understanding has been lost, their moral sense has become dead, and while following this way they never even feel that their habit of always telling lies, their deceitful behaviour and the ever present contradictions between their word and deed is a wretched state in which they have involved themselves. This is one of those verses in which the meaning of ';causing a seal to be set on the heart of somebody by Allah" has been made clear. These people did not become hypocrites because Allah .had set a seal on their hearts; so faith did not enter them, and they became hypocrites under compulsion. But, in fact, Allah set a seal on their hearts only when they decided to persist in disbelief in spite of professing the faith outwardly. Then, they were deprived of the capacity to believe sincerely and of the grace of the moral attitude resulting from it. and were helped to persist in the hypocrisy and hypocritical morals, which they had chosen to adopt for themselves.
 

That is because they believed, and then they disbelieved; so their hearts meaning in Urdu

یہ سب کچھ اس وجہ سے ہے کہ ان لوگوں نے ایمان لا کر پھر کفر کیا اس لیے ان کے دلوں پر مہر لگا دی گئی، اب یہ کچھ نہیں سمجھتے