Envy (Hasad) means resenting the blessings of Allaah that are enjoyed by the one who is envied, and wishing that it be taken away. In other words, the envier wishes that the blessing be taken away from the one whom he envies, whether the blessing comes to him or not.
So the envier resents the blessing of Allaah and wishes that it be taken away, and he may even make efforts to take it away.
Evidence for the existence of envy:
“Many of the people of the scripture (Jews and Christians) wish that if they could turn you away as disbelievers after you have believed, out of envy from their ownselves, even after the truth (that Muhammad is Allaah’s Messenger) has become manifest unto them.” (Al-Baqarah 2:109)
Evidence from the Sunnah:
Al-Tirmidhi narrated that the freed slave of Al-Zubayr (Radhi Allaahu Anhu) said: The Messenger of Allaah (Peace be upon him) said:
“The disease if the nations who came before you has started to spread among you: jealousy and hatred. This is the ‘shaver’ (destroyer); I do not say that it shaves hair, but that it shaves (destroys) faith. By the One in Whose Hand is my soul, you will not believe until you love one another. Shall I not tell you that which will strengthen love between you? Spread (the greeting of) Salaam amongst yourselves.” (Al-Tirmidhi 2510.)
Characteristics of the envier:
The envier is always angry at the decree of Allaah.
The envier always complains and rarely thanks Allaah even if he owns the whole world.
He follows up the mistakes of the one whom he envies, and tries to seek out his faults, and exposes them and exaggerates about them before others.
He conceals or ignores or belittles the good qualities and distinguishing characteristics of the person whom he evies.
So you will notice that the envier cannot speak in front of the one whom he envies without addressing him in a laughing, jocular manner, but deep down he is filled with hatred and resentment that is clear from the way in which he looks at him.
He clearly criticizes the one whom he envies, with or without evidence.
He looks for opportunities and makes the most of any chance to harm the one whom he envies in himself or his wealth.
Finally, the envier is a troubled man, due to the resentment that is always festering in his heart, so depression and dullness show on his face.