A. Envy (Hasad) is desiring the removal of a blessing from one truly deserving it.
Al-Munawi, al-Tawqif
الحسد تمني زوال نعمة عن مستحق لها – المناوي

A.1. The Relationship Between Envy and Miserliness

Envy and miserliness are related in that their possessor desires to deny a blessing to someone else. The miser is distinguished by not wanting to share a blessing with someone else, and the envious person desires that no one other than himself is given a blessing.
Al-Kafawi, al-Kulliyyat

A.2. Ten Cures for Envy
1. Seeking refuge with Allah from its evil.
2. Being conscious of Allah (Taqwa).
3. Patience with one’s social enemy [by not retaliating against him].
4. Relying on Allah, for whosoever relies on Allah, He suffices him.
5. Emptying the heart of being preoccupied with or thinking about her [the object of one’s envy].
6. Orienting oneself towards Allah, being sincere with Him, placing His love, pleasure and penitence to Him in the place of fleeting thoughts of the soul and its baseless aspirations.
7. Having pure repentance to Allah from the sins his enemies have led him to commit.
8. Giving charity and engaging in acts of goodness to the extent possible, because that has an amazing effect in repulsing tribulations, the evil eye, and the wickedness of the envious person.
9. This is the most difficult cure for the ego, and the weightiest upon it. No one is given the providence to undertake it except one whose portion [of spiritual strength] from Allah is great. It is extinguishing the fire of envy, iniquity, and harm by extending good to the envious person.
10. This is the compendium of all of the other cures; they all revolve around it. Namely, pure divine unity, and elevating your thought from the effects manifested in creation [something envy revolves around] to the mighty, wise cause of those effects.
Ibn Qayyim al-Jawziyya, al-Tafsir al-Qayyam
A.3. Texts from The Qur’an and the Sunnah Concerning Envy

ود كثير من أهل الكتاب لو يردونكم من بعد إيمانكم كفارا حسدا من عند أنفسهم من بعد ما تبين لهم الحق فاعفوا واصفحوا حتى يأتي الله بأمره إن الله على كل شيء قدير

Many of the People of Scripture would love if they were able to turn you back to disbelief after your faith, out of the envy they harbor in their souls; after the truth has been made clear to them. Pardon, and overlook [their faults] until Allah brings about His command. Surely, Allah has power over all things.
Qur’an 3:109

أم يحسدون الناس على ما آتاهم الله من فضله فقد آتينا آل إبراهيم الكتاب و الحكمة و آتيناهم ملكا عظيما

Do they envy people over what Allah has given them from His bounty? We have given the Family of Abraham the Scripture and Wisdom; We have given them a great dominion.
Qur’an 4:54

The Prophet, peace upon him, has said, “Surely, the disease of the nations will afflict my community.” They said, “What is the disease of the nations?” He said, “Arrogance, iniquity, consumerism, vying over the world, mutual alienation, and envy; until there is rebellion and then widespread murder.”
Ibn Abi al-Dunya

The Prophet, peace upon him, said, “Beware of suspicion, for surely suspicion is the worst form of lying; do not eavesdrop on one another, do not spy on one another, do not vie with one another, do not envy one another, do not hate one another, do not break relations with one another, be you servants of Allah, brothers.”
Bukhari, #6066

The Prophet, peace upon him, mentioned, “The people will be in good shape as long as they do not envy one another.”
Mundhari, al-Targhib wa’l Tarhib, 3:574

A.4. Sayings of the Scholars Concerning Envy

“There is no vile characteristic more just than envy. It destroys the envious person before his harm reaches the object of his envy.”
Mu’awiya, Adab al-Dunya wa’l Din

“No servant remembers death frequently except that his gaiety and envy are drastically reduced.”
Abu al-Darda’, al-Ihya’

“Why are you envying your brother? If what he has been given is because of his nobility, why are you envying one Allah has ennobled? If [what he possesses] is for some base reason, why are you envying one whose destination is Hell?”
Al-Hasan, al-Ihya’

“Envy is the first sin committed against Allah in heaven; that is Iblis envying Adam. And it is the first sin committed against Allah on earth; that is the son of Adam envying his brother until he murdered him.”
Anonymous, Adab al-Dunya wa’l Din

“People are of two types, enviers and the object of their envy; and every blessing has an envier.”
Anonymous, Adab al-Dunya wa’l Din