Is it obligatory for a fasting person to make up for their fast if they believed it was invalidated due to engaging in a prohibited act, but then it later became clear to them that their fast was not invalidated?

If a fasting person believes their fast has been invalidated, but then refrains from eating for the rest of the day out of respect for the month, and it later becomes clear that their fast was not invalidated, then no قضآء (making up the fast) is required of them. This is because they did not do anything that contradicts the fast, nor did they intend to break it. Therefore, their fast is valid and sufficient. This is the fatwa (definition) issued by the two Shaykhs, Ibn 'Uthaymeen and Ibn Jibreen.