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."
Hadith Referenceصحیح ابن حبان / كتاب الصوم / 3583
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «التعليق» -أيضا-.فضيلة الشيخ العلّامة شُعيب الأرناؤوطإسناده صحيح على شرط مسلم
Sayyiduna Abu Musa Ash'ari (may Allah be pleased with him) narrates this statement of the Prophet (peace and blessings of Allah be upon him): "Whoever always (i.e., daily observes voluntary fasting), Hell will be made so narrow for him." The Prophet (peace and blessings of Allah be upon him) indicated this by making the figure of ninety. The narrator named Fadl narrated these words the second time: "The Prophet (peace and blessings of Allah be upon him) closed his fist at ninety." (Imam Ibn Hibban, may Allah have mercy on him, says:): In this narration, what is meant by always fasting is: to fast even on the days of Tashreeq and the two Eids, and there is severe condemnation for the person who always fasts and also fasts on those days in which fasting is prohibited. This does not mean that the person who always fasts, and he has the strength for it, but he does not fast on those days in which fasting is prohibited, will also be punished on the Day of Resurrection. Abu Tamimah Hijimi's name is Tarif bin Mujahid; he was a resident of Basra. He passed away in 95 Hijri.
Hadith Referenceصحیح ابن حبان / كتاب الصوم / 3584
Hadith Gradingفضيلة الشيخ الإمام محمد ناصر الدين الألبانيصحيح - «الصحيحة» (3202).فضيلة الشيخ العلّامة شُعيب الأرناؤوطحديث صحيح