What is the ruling regarding the divorce of a father who divorced his wife six times, then followed that with a triple divorce in the same sitting, knowing that he does not pronounce the letter ط (ṭāʾ) as ت (tāʾ), and that he had previously divorced her twice and taken her back after her waiting period (ʿiddah) with a new mahr?

What your father uttered, namely the repetition of the explicit divorce pronouncement six times, followed by his pronouncement of triple divorce in a single sitting, all of this results in a major irrevocable divorce (according to the opinion we rule by). If he intended to repeat the divorce, then three divorces have occurred. If he intended emphasis and not repetition, then she has become irrevocably divorced from him by the collective pronouncement of triple divorce. So, if he said, "You are divorced, you are divorced," two divorces are binding upon him, unless he intended by the second pronouncement to make her understand that the first had occurred, or to emphasize, in which case it counts as one divorce. If he had no intention, two divorces occur. If he pronounced three divorces in one word, all three divorces occur, and she becomes unlawful for him until she marries another husband. This is the opinion of the majority of jurists. As for the father pronouncing the letter "taa’" instead of "ṭā’," this does not prevent the divorce from occurring according to the Hanafis and others, unless he denies that he intended divorce by this utterance, in which case he is to be believed religiously, but not judicially, unless he calls witnesses to his lack of intention to divorce.