Hadith: “The Sawm (fast) is a shield (against all sins).” (Nasai and Tirmidhi)
It is mentioned in 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.
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.
As 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.