Is a husband who doubts his utterance of ẓihār to his wife obligated to ask her, or should he dismiss the doubt and base his decision on certainty, especially if he is prone to doubts?

The principle of "certainty is not removed by doubt" addresses the whispers (waswas) concerning purity, prayer, divorce, and zihar (a form of divorce-like utterance). Thus, whoever doubts their divorce is not bound by its ruling, because the marriage is established with certainty and is not removed by doubt. Therefore, one must cast away these doubts and not pay attention to them, and fight against the waswas by turning away from them and ignoring them after frequently remembering Allah and seeking His help.