The Messenger of Allah (sal Allahu alaihi wa sallam) said: “There are many fasting men who do not gain by fasting except hunger and thirst.” On being asked the reason he said: “He refrains from eating lawful food but breaks fast by eating human flesh by back-biting. That is unlawful.” [Ihya Ulum Id-Deen]

There is nothing to be gained from fasting if it is kept with lawful food but broken with unlawful food (human flesh). Allah (subhana wa ta’ala) has equated back-biting with eating human flesh. “Do not back-bite one another. Does one of you like that he eats the flesh of his dead brother? You would abhor it.” [Quran: Al-Hujraat, Ayat 12]

He who fasts and commits the evil deed of back-biting is like a patient who restrains himself from eating fruits for fear of disease but who swallows poison. A sin is like eating poison. He who drinks this poison is a fool. [Ihya Ulum Id-Deen]Source:dailyhadith.adaptivesolutionsinc.com