Is it obligatory to repeat the ‘Isha prayer after gaining certain knowledge that one’s ablution was nullified during it, and what is the ruling if a person doubts the nullification of his ablution after having been certain of it at the time?

We ask God to cure you of whisperings (waswas) and advise you to ignore them. A person afflicted with whisperings relies on the first thought that occurs to him and disregards what comes after. So, if you are certain that your ablution was nullified during prayer, the prayer becomes invalid, and you must make it up after performing ablution anew. However, if you have a doubt about the invalidity of your ablution, do not pay attention to it, and you remain in a state of purity, for purity is not nullified except by certainty. And if you become certain of the invalidity of your ablution, and then later have a doubt about its invalidity, the ablution is indeed invalid.