Mutarrif bin Abdullah narrates from his father that the Prophet Muhammad (peace be upon him) said: "Whoever always (i.e., daily) observes voluntary fasting, in reality, he has neither fasted nor left fasting." (Imam Ibn Hibban, may Allah have mercy on him, says:) The statement of the Prophet Muhammad (peace be upon him), "Whoever always fasts, in reality, he has neither fasted nor left fasting," means: whoever always fasts and among those days are included the days on which fasting is prohibited, such as the days of Tashreeq and the days of Eid. (The words of the narration) "he has neither fasted nor left fasting" mean: he has neither always fasted so that he may be rewarded for it, because he could not avoid the sin which he committed by fasting on the prohibited days. Therefore, the Prophet Muhammad (peace be upon him) said: "For the one who always fasts, Hell becomes narrow in this way." The Prophet Muhammad (peace be upon him) indicated this by making the number ninety. By this, he meant: Hell becomes narrow for him because of his fasting on those days in which fasting is prohibited."