That is because they believed, and then disbelieved; therefore their hearts are sealed, so they understand not.meaning, He has decreed them to be hypocrites because they reverted from faith to disbelief and exchanged guidance for misguidance. Therefore, Allah stamped and sealed their hearts and because of it, they cannot comprehend the guidance, nor any goodness can reach their hearts. Truly, their hearts neither understand, nor attain guidance.Allah said