Actions affect us in different ways. Generally good actions bring positive effects and bad actions bring about negative effects on the soul. It sometimes happens that the positive effect of an action becomes null, or even damaging because of something we do. Fasting in Ramadan is a good example. To fight the desires of the ego is good and it will in sha Allah affect us in a positive way, but if we totally give in to our desires by Maghrib, then the effort made during the day obliterates the good effects. Imam al-Ghazali writes:
“It is well known that the object of Fasting is to experience hunger and to check desire, in order to reinforce the soul in piety. If the stomach is starved from early morning till evening, so that its appetite is aroused and its craving intensified, and it is then offered delicacies and allowed to eat its fill, its taste for pleasure is increased and its force exaggerated; passions are activated which would have lain dormant under normal conditions.” (Inner dimensions of Islamic worship p. 78, translation by Muhtar Holland)
In the Quran Allah uses the word حبط to describe the obliteration of previous actions:
They are those who deny the Signs of their Lord and the fact of their having to meet Him: vain will be their works, nor shall We, on the Day of Judgement, give them any weight. (Q. 18:105, Yusuf Ali)
According to Ahmad ibn Faris the root ح ب ط has one original meaning referring to a state of being null or in pain. “Being null” has been mentioned above, i.e. good works being null or in vain. As for pain the origin comes from the physical pain that is experienced by an animal that eats too much and, as a result, becomes swollen or inflated by the food.
The link between pain and being null is obvious. The good effect that food usually has, turns into something bad and causes pain when it’s not eaten with moderation.
The same is true for fasting. Even though the fast is valid from a fiqhi-perspective, the positive effects are obliterated by excessive eating.