That namely their evil deed is because they believed by affirming faith only with the tongue then disbelieved in their hearts that is to say they persist in harbouring disbelief in it; therefore their hearts have been stamped sealed with disbelief. Hence they do not understand faith.
- 63:33
ذَٰلِكَ بِأَنَّهُمْ آمَنُوا ثُمَّ كَفَرُوا فَطُبِعَ عَلَىٰ قُلُوبِهِمْ فَهُمْ لَا يَفْقَهُونَ
That is because they came to believe, and then renounced (their faith). So their hearts were sealed; and now they do not understand.
- common.revelation-Medinan
- common.hizb : 221