Is it permissible to interrupt post-prayer remembrances – such as tasbih (subhan Allah), tahmid (alhamdulillah), and takbir (Allahu akbar) – to return a greeting or answer one's parents, and then resume them, or is it obligatory to continue without interruption? And what should be done in case of error or doubt in counting?

The original principle regarding post-prayer supplications (dhikr (definition)) is that they should be consecutive without interruption, based on the apparent meaning of the hadiths. However, it is permissible to interrupt the dhikr for an urgent matter, such as returning a greeting, saying "Yarhamukallah" to someone who sneezes, or answering one's parents. The person performing dhikr should then resume their recitation. This is better than continuing the dhikr uninterruptedly and missing the urgent matter. If the interruption is long, however, it negates the virtue of performing dhikr immediately after the prayer.

As for someone who makes a mistake in counting the dhikr or doubts its number, they should base their count on certainty, which is the lesser number. For instance, if they doubt whether they have completed thirty-three or thirty-two tasbihs, they should consider it thirty-two, because the lesser number is what is certain.