Hasad (jealousy and envy) is among the most destructive emotions or feeling which a man may have towards his fellow human being. It causes him to wish evil for others and to be happy when misfortune befalls them. The Prophet (sallallahu alaihi wa-sallam) warned against envy by comparing it to fire that completely burns the wood.
He (sallallahu alaihi wa-sallam) said: “Beware of jealousy, for verily it destroys good deeds the way fire destroys wood.” [Abu Dawood]
Hasad is a disease of the heart and it causes impurity to the heart, when Allah’s Messenger (sallallahu alaihi wa-sallam) was asked who are the best of people? He (sallallahu alaihi wa-sallam) replied: “the one with a clean heart and truthful tongue.” They asked: ‘We understand a truthful tongue, but what does a clean heart mean?’ he answered: ‘It is the heart of one that is pious, pure, and is free of sin, transgressions, hatred and Hasad.”
[Ibn Majah]
Hasad is such a dangerous characteristic that Allah revealed verses of the Qur’aan to be recited as a protection from the jealous, “Say: I seek refuge in the Lord of the dawn..(till).. From the evil of envious when he envies.” [Soorah al-Falaq (113)]
Narrated Al-Zubayr Ibn al-Awam that the Prophet (sallallahu alaihi wa-sallam) said: “There has come to you the disease of the nations before you, jealousy and hatred. This is the ‘shaver’ (destroyer); I do not say that it shaves hair, but that it shaves (destroys) faith” [(Hasan) Jamee at-Tirmidhee]