Allah, the Wise, has said:
أَمْ يَحْسُدُونَ النَّاسَ عَلى ماَ آتاَهُمُ اللٌّهُ مِنْ فَضْلِهِ
"Or do they envy the people for what Allah has given them of His grace?" 
Imam Sadiq (as) has said:
إِنَّ الْمُؤْمِنَ يَغْبِطُ وَ لاَ يَحْسِدُ.
"A true believer exults, but never envies."
Envy stems from blindness of the heart and rejection of Allah's grace - the two wings of kufr and disbelief. An envious person's evil afflicts him before it can afflict the envied; just like Iblees, whose evil overtook his own self and made him the eternally accursed one, whereas Adam went on to attain the rank of Prophethood.
The balance (of deeds) of a jealous person is light, thereby making Hell his abode, whereas the balance (of deeds) of the envied person is heavy, thereby leading him to Paradise. In view of this, Qabeel, who had murdered his brother Habeel because of this vice, hurled himself in Hell while sending his brother to Paradise.
If this vice penetrates into the soul of a person, he would never be able to repent (for his misdeeds) but instead, would always be on the lookout to cause harm and injury to those, who are either superior to him or possess more than him.
1 – The Friend of aIsa
Imam Sadiq (as) said: "Stay away from jealousy and do not harbour envy with respect to one another." Having said this, the Imam (as) continued: "One of the practices which Prophet aIsa (as) adopted for himself, was to travel from city to city. During one of these journeys, he took along with him a companion who was of short build and who also happened to be one of his attendants.
After a while, they reached the sea. aIsa (as) recited the name of Allah, stepped onto the water and began walking over it effortlessly. Repeating what aIsa (as) has performed, the companion recited what the prophet had and began to follow him over the water. In the middle of the sea he thought to himself, "aIsa is a prophet and walks over water and I am walking over water too, so what superiority does he possess over me?"
These thoughts hardly crossed his mind when he suddenly fell into the water and began to plead to aIsa (as) for help.
aIsa (as) took hold of his hand and pulled him out of the water.
"What did you say that caused you to fall into the water?" he asked. The companion confessed to the thoughts that had passed through his mind.
"You placed yourself in a position other than what Allah had ordained for you, thus becoming the object of His wrath," remarked aIsa (as). "Seek forgiveness so that you regain your previous rank once again."
As soon as the companion sought forgiveness, he began to follow aIsa (as) over the water once again."
After narrating this incident, Imam Sadiq (as) advised: "Fear Allah and avoid jealousy."
2 – Abdullah Ibn Ubayy
As the people of Madinah were accepting the Noble Prophet (sa) in increasing numbers, Abdullah Ibn Ubayy, one of the Jewish elders, became even more envious towards the Noble Prophet (sa), and thus planned to kill him.
He invited the Noble Prophet (sa), Ali (as) and the other companions for his daughter's wedding-feast. Meanwhile, he had a huge pit dug up in the courtyard of his house, filled its base with swords, arrows and lances, and had it covered up with a carpet. In addition to this, he poisoned the food and also concealed some Jews, armed with poisoned swords, in the house. His idea was that when the Noble Prophet (sa) and his companions walked towards the pit, they would fall into it whereupon the armed Jews would rush out and put them to death. He had poisoned the food so that should this plan fail, they would be killed by means of the poison.
Jibra`il, through the orders of Allah, revealed these two plans which stemmed from jealousy and envy to the Noble Prophet (sa) and said to him: "Your Lord says: Go to Abdullah Ibn Ubayy's house and sit wherever he requests you to sit and eat whatever he presents before you, for I shall suffice you and protect you from his evil designs."
The Noble Prophet (sa), Amirul Mo'minin (as) and the other companions entered Abdullah's house. Abdullah ushered them to the courtyard of his house. As per his request, all of them sat over the pit but nothing happened, much to Abdullah's astonishment.
He then ordered the poisoned food to be brought. When it was placed before them, the Noble Prophet (sa) told Ali (as) to recite the following over the food: "In the name of Allah, The Healer; in the name of Allah, The Sufficient; in the name of Allah, The Acquitter; in the name of Allah, with Whose name no thing or sickness, in the earth or in the heaven, can cause harm, and He is the All-Hearing, the All-Knowing."
Then, all of them ate the food and came out of the gathering without being harmed in the slightest. Abdullah's bewilderment knew no bounds; he assumed that the food had not been poisoned and so ordered the armed Jews to eat it, as a result of which, all of them died.
Meanwhile, his daughter who was the bride, decided to sit down on the carpet covering the pit. As soon as she did so, she plummeted into the pit. Her shrieks filled the air, only to subside with her death.
Abdullah ordered his servants not to reveal the cause of all the deaths in the house. When the news of these incidents reached the Noble Prophet (sa), he asked the jealous Abdullah what had happened.
"My daughter fell off the roof of the house; as for the others, they died due to diarrhoea," he replied.
3 – The Strange Act of the Envious Person
During the caliphate of Hadi Abbasi, there lived in Baghdad a wealthy person who was righteous and beneficent. In his vicinity, there resided a person, who was envious of his wealth, and no matter how much he tried to taint the wealthy person's prestige and bring him into disrepute, he could not succeed. Finally, he decided to purchase a slave, train him and then use him to implement his evil intention.
One day, after a year had passed, he asked his slave: "How obedient are you to your master?"
The slave replied, "If you ask me to hurl myself into the fire, I shall do so." The man was overjoyed to hear this.
"My neighbour is rich and wealthy and I bear animosity towards him. I want you to carry out my instructions. Tonight, both of us shall climb onto the roof of his house where you will kill me so that he is accused of my murder and is put to death by the government as a punishment for killing me," he said to the slave.
However much the slave insisted on not carrying out these instructions, it was to no avail and the man remained unyielding. At midnight, as per the orders of his envious master, the slave severed his master's head on top the roof of the rich neighbour and hurried back to his bed.
The next day, the death of the jealous person came to light and Hadi Abbasi had the rich person arrested, and subjected him to interrogation. He then summoned the slave and interrogated him too.
The slave, observing that the rich person was totally innocent, divulged the incident of jealousy and the subsequent killing. Hearing the incident, the Caliph lowered his head, reflected for a while and then raised it again.
"Although you have killed a person, you exhibited courage and saved an innocent person from accusation, therefore, I shall set you free," the Caliph said to the slave.
In this manner, the harm of envy and jealousy rebounded upon the envious person himself.)
4 – The Envy of the Womenfolk
Ibn Abi Laila was the judge during the caliphate of Mansur Dawaniqi.
"Many strange and interesting cases are brought before the judges and it is my desire that you relate one of them to me," Mansur said to him.
Ibn Abi Laila related: "One day an old and humble lady approached me and implored me to defend her right and punish her oppressor. I asked her who she wanted to complain about.
She replied, "My niece."
I ordered the niece to be brought before me. When she arrived, I observed that she possessed charming looks and an appealing physique. I asked her the reason for her aunt's complaint whereupon she related the entire case as follows: "I am the daughter of this old woman's brother and she is my aunt. My father died while I was still a child and this aunt of mine took care of me and was never negligent with respect to my upbringing. When I grew up, with my consent, she married me to a goldsmith.
My comfortable life made my aunt envious of me. She ornamented her daughter and brought her before my husband, who became captivated by her and sought her hand in marriage.
This aunt of mine stipulated that she would marry her daughter to him only if the authority to retain or divorce me was placed in her hands. My husband agreed to this condition.
"After a period, my aunt had me divorced and I separated from my husband. Meanwhile, my aunt's husband, who had been away on a journey, returned home. After realising what had happened, he used to console me. I presented myself to him in such a manner that he found me attractive. Eventually, he fell for me and expressed his desire to marry me.
I said to him, "I shall only agree upon the condition that the authority of divorcing my aunt be placed in my hands."
"He agreed and after the marriage, I had my aunt divorced and I continued to live with this husband, who died after a period of time. One day, my first husband approached me and expressed his inclination to marry me again.
"I am willing to marry you again but upon the condition that you should grant me the authority to either retain or divorce my aunt's daughter," I told him.
He accepted and once again I got married to my first husband and, with the authority vested in me, I also had my aunt's daughter divorced.
Now you can judge that I have committed no offense; all that I have done is to recompense the baseless envy of this aunt of mine." 
5 – The Consequence of Jealousy
Once, during the Caliphate of Muatasim Abbasi, a learned person arrived in his court.
Muatasim was so impressed with his talks and speeches that he ordered him to come to the court every few days. The man used to come regularly and before long became one of the confidants of the Caliph. Another of the Caliph's confidants became jealous of this person and fearing that he would take over his ministry, considered ways of getting rid of him.
One day, at the time of Dhuhr, as he was leaving the Caliph's gathering together with the learned person, he requested him to accompany him to his house so that they could talk and have lunch together. The learned man accepted his request.
When they sat for lunch, garlic was also served with the food and the man consumed a lot of it. At the time of Asr, the jealous person proceeded towards the Caliph and said: "As I am burdened by your favours and bounties, I cannot conceal this secret from you. This learned man who is your confidant, has been secretly complaining to the people that the foul odour from the Caliph's mouth is killing him but the Caliph repeatedly summons him to go to him."
The Caliph was horrified to hear this and ordered the learned man to be brought before him. Since he had consumed a lot of garlic, he covered his mouth with a handkerchief and sat at a distance from the Caliph. Observing this, the Caliph became certain of the truthfulness of the minister's words. He wrote a letter to one of his assistants instructing him to kill the bearer of that letter and he asked the learned man to take it to the assistant.
The jealous confidant was waiting outside the room. As soon as the man came out of the Caliph's court with the letter in his hand, the confidant thought that the letter contained the Caliph's orders for a large sum of money to be given to him, and this added fuel to his already flaming envy. He offered two thousand dirhams to the man in return for the letter. The learned man accepted the money and also accepted the confidant's request not to go to the Caliph for a few days.
The jealous confidant took the letter to the Caliph's assistant who immediately beheaded him. Some days later, the Caliph enquired, "Where is the learned man? Has he gone on a journey?"
Those around him said, "No, we have seen him just recently." The Caliph ordered that he be brought before him. When he had arrived, the Caliph, with great astonishment, inquired: "I had given you a letter to hand over to my assistant, did you not do as instructed?"
The man recounted the incident of the letter and the jealous minister.
The Caliph said, "I shall ask you a question; do not lie. Did you tell my confidant that the foul odour from the Caliph's mouth troubled you?" The learned man replied in the negative.
"Why then did you sit away from me when you last came to see me and covered your mouth with a handkerchief?" asked the astounded Caliph.
"Your confidant had taken me to his house and fed me garlic and so when I arrived in your presence, I feared lest the odour should inconvenience you," replied the man.
Hearing this, the Caliph uttered, "Allahu Akbar!" and then related the whole incident to those present around him. All of them were left astonished and amazed.
 Noble Qur'an, Suratul Nisa (4), Verse 54
 Jamea al-Saaadat, Volume 2, Page 195
 Tadhkeratul Haqaiq, Page 49
 Shanidani-ha-e-Tarikh, Page 316; Mahajjatul Baiza, Volume 5, Page 328
 Khazinah al-Jawahir, Page 344; Biharul Anwar, Volume 6
 He was the brother of Harun al-Rashid and was the caliph for almost a year after which, the caliphate reached Harun.
 Dastan-ha-e-Ma, Volume 2, Page 138; Mustadrakul Wasa`il, Volume 3 (In the biography of Fazlullah Rawandi
 Pand-e-Tarikh, Volume 2, Page 156; Ialam al-Nas (of Atlidi), Page 44
 Rangarang, Volume 1, Page 358