Is the prayer of a person afflicted with obsessive doubts (waswas) valid if he doubted his ritual purity (hadath) during ablution and then again during prayer, while remaining indecisive, or must he repeat it?

The correct approach is to disregard obsessive doubts and uncertainties in prayer and not to pay attention to them. These obsessive whispers do not harm or affect the validity of the prayer, and it is not obligatory to repeat it. This is because the default is the validity of purification, and certainty is not removed except by certain impurity, as the Prophet, peace and blessings be upon him, said: "He should not leave until he hears a sound or perceives a smell."