Some devoted believers may wish to fast forever, oblivious to hardship in their life, not to mention the fact that this type of fasting is not in harmony with the spirit of Al-Islam. When reports of Abdullah Bin `Amru's continuous fasting reached the Messenger of Allah (saas), Abdullah related later:
"The Messenger told me, `I have been informed that you observe night prayer and a daily fast.' Ibn Amru answered, Yes!' O Messenger of Allah. The Messenger advised him: `Fast a day and break a day. Pray at night and sleep. For your body has rights over you, your wife has rights over you, and your guest has rights over you. Indeed, it will perfectly suffice for you to fast three days every month.' Amru strongly pointed out that he was capable of observing the fast of the fashion he was doing. But Messenger advised against it. Ibn Amru said, `Then I explained to him that I have the strength to do it.' The Messenger of Allah (saas) then said: `Observe three days fasting starting from Friday (and then break).' Ibn 'Amru said: `I strongly stressed to him that I could, and he vigorously said I should not.' The Messenger of Allah then instructed, `Observe your fast as the Prophet of Allah, Dawud, (David, ass), used to observe and do not exceed it. `How did he fast?' 'Amru asked. The Prophet (saas) said: `Prophet Dawud (ass) used to fast a day and break the next.'" (Ahmad)
This hadith is instructing and revealing that the objectives in the command to fast are not to unduly injure, or deny the body the natural way of living. It also indicates the caring side of this Messenger of mercy as he tried to convince Amru that his decision to spend the rest of his life in fasting was not in harmony with Islam. With continuous fasts, one loses the physical and spiritual benefits. Physically, because it becomes a routine and the body loses the benefits of the way the fast is structured. Spiritually, one feels the numbness, and boredom of the heart. The spouses' right to marital association is denied as continuous fasting decreases sexual desire.
The soul is affected only by what intrudes upon it, not by what it is accustomed to. Do you not see that the doctors will advise a person not to take a drug, as a matter of routine, unless the body needs it, lest the same drug will be ineffective when the person gets sick?
The hadith indicates that no one has the right to use his or her body exclusively in the way they desire. In every undertaking, one should bear in mind the other legal rights. The responsibilities of a person are multiple. For while you may think you are worshipping Allah, you may well be violating Allah's rules, because you lose the balance in worship by infringing on the rights of your body when you overly deny it the element of survival.
If you fail to fulfill the marital covenant towards your wife or husband, you may be making her or him vulnerable and susceptible to unlawful, immoral acts. The Hadith also reveals and indicates the beautiful relationship between the teacher and the student, and how the Messenger was very patient with a companion who had unlimited energy and did not mind spending it fasting. It reveals how the Prophet (saas) encouraged the believers to express their opinions and ask questions while observing the etiquette of respect to the Messenger of Allah (saas) who said: "The best (voluntary fast in the sight of Allah) is the fast of Prophet Dawud, and the best nightly voluntary prayer is the prayer of Prophet Dawud." The Messenger explained, "He used to sleep half of the night then pray one-third of the night, then sleep one-sixth of the night. In fasting, he used to fast a day and break the next." (Ahmed)
It is a mercy from Allah (SWT) that our Prophet Muhammad (saas) is in tune with all the previous revelations' as we see in Al-Qur'an and the Sunnah. It is rich spiritual information made available through him (saas) to this Ummah.