What is the criterion for a doubt to be considered persistent (mustankah) if I doubt whether the doubt occurred to me today or not? And for how many days must the doubt occur for it to become persistent after an interruption? And should I give in to the waswās (whispers/obsessive thoughts) if it does not come to me every day, such as repeating the takbīrat al-iḥrām when in doubt about its pronunciation? And what is the ruling on a persistent doubt if it occurs one day and is absent another?

It appears that the questioner is afflicted by waswasah (obsessive whispering/doubts). Waswasah differs from doubt (shakk). One afflicted by waswasah should completely disregard it and pay no attention to it whatsoever. As for doubt (shakk), it is not to be ignored unless it becomes chronic (mustankih). Ibn Hajar al-Makki differentiated between waswasah and doubt by stating that doubt is accompanied by a sign, whereas waswasah is the judgment of impurity without any sign, or the estimation of something that has not occurred. Therefore, the questioner must completely disregard these waswasah.