1. Rasulullah Sallallahu alayhi wasallam said: "The sleep of a fasting person is regarded as an act of ibaadah, his remaining silent is regarded as a tasbeeh (that is. when the fasting person remains silent, he receives the reward of reciting Sub'haanallah which means ‘Glory be to Allah’), the reward for his good deeds is multiplied, his duas are accepted (fasting has a special influence on the acceptance of duas.), and his sins are forgiven."
2. It is mentioned in a Hadith that fasting is a shield and a strong fortress in order to save oneself from hell. In other words, just as a person seeks refuge in a strong fortress or by means of a shield from an enemy, in the same way, one gets salvation from hell by fasting. By fasting, a person's power of committing sins gets weak, and his power to do good gets stronger. When a person fasts in the proper manner and implements all the etiquette of fasting, he will free himself of sins and gain salvation from hell.
(When a person fasts he makes it Waajib upon himself to abstain from nourishment and conjugal relations. Food and conjugal relations are not only halaal but are infact crucial for the existence of humankind. Thus that person who leaves halaal out of Imaan and love for Allah Ta’ala, will automatically be protected from falling into haraam. If he is fasting with sincerity, he will think twice before engaging in any haraam sinful act. The fasting is thus like a fortress and a shield protecting him from the frontline of the enemy. This is also a gauge for us to determine if we are fasting with sincerity and being protected from haraam or not. - Publisher)
3. It is mentioned in a Hadith that fasting is a shield as long as it is not destroyed by lies and backbiting. In other words, fasting works as a shield as explained above. But this is on the condition that the person abstains from sinning. If a person fasts and still speaks lies, backbites, and commits other sins, then although he will be absolved of the fard of fasting, he will be committing a major sin. Furthermore, he will be deprived of the barakah of fasting.
4. It is mentioned in a Hadith that fasting is a shield. The person who awakens in the morning in a state of fasting should not commit any act of ignorance. If a person approaches him in an ignorant way, he should not reply him in the same ignorant manner nor should he address him disrespectfully. Instead, he should inform him that he is fasting. By him in whose control is the life of Muhammad Sallallahu alayhi wasallam, the smell that emanates from the mouth of a fasting person is more beloved in the sight of Allah Ta'ala than the fragrance of musk. In other words, on the day of judgement, the smell that emanates from the mouth of a fasting person will be replaced with a fragrance even better than musk. This fragrance will emanate from the mouth of the fasting person and it will be most beloved in the sight of Allah Ta'ala. This foul smell that emanates from a fasting person in this world will actually be a source of attaining that fragrance in the hereafter.
Source: Bahishti Zewar