The Meaning of Extravagance and Wastefulness
Israf linguistically: israf and saraf is overstepping moderation. Asrafa fi malih is a statement meaning that one rushedly and immoderately spent one’s wealth. Israf in expenditure is wastefulness.  Lisan al-`Arab, Ibn Manzur (9/148)
Israf technically: is transgressing limits in everything one does, though it is most commonly used when referring to spending wealth.  al-Mufradat, al-Raghib (p. 407).
Tabdhir linguistically: is splitting up a thing. It originally refers to the throwing of seeds and spreading them out, and then got used to refer to any one who wastes his wealth. Badhdhara malah means that one spent his wealth corruptly and extravagantly.  al-Mufradat, al-Raghib (p. 114); Lisan al-`Arab, Ibn Manzur (9/148).
Tabdhir technically: is spending wealth in other than its right, and expenditure in what ought not be spent in.  Tafsir al-Qurtubi (10/247); al-Ta`rifat, al-Jurjani (p. 24); al-Klliyyat, al-Kafawi (p. 113). The Difference between Extravagance (Israf) and Wastefulness (Tabdhir)
❖ Extravagance is spending wealth in a valid outlet but in invalid amounts. Wastefulness is spending wealth in invalid outlets.  al-Ta`rifat, al-Jurjani (p. 24).
❖ Malik said: “Extravagance is taking wealth from where it ought to be spent and placing it where it ought not to be. It is wastefulness.”  Tafsir al-Qurtubi (10/147). Dispraise of Extravagance and Wastefulness in the Qur’an and Sunnah
❖ Allah, exalted, says: “Eat from the fruit they bear and pay the dues at harvest, but do not waste. Surely, He does not like the wasteful.” al-An`am: 141.
❖ Allah, exalted, says: “Children of Adam, dress properly whenever you are at worship. Eat and drink, but do not waste. Surely He does not like the wasteful.” al-A`raf: 31.
❖ Allah, exalted, says: “Give to close relatives their due, as well as the poor and the needy travellers. Do not spend wastefully. Surely, the wasteful are brothers to the devils. And the Devil is ever ungrateful to his Lord.” al-Isra’: 26 - 27.
❖ The Messenger of Allah ﷺ said: “Eat, drink, give charity, and dress well so long as all of that is not mixed with extravagance or arrogance.”  Reported by al-Nasa’i (2559) and Ibn Majah (3605) and this is his wording. Ibn Hajar graded it as sound in al-Amali al-Mutlaqah (32), and Ahmad Shakir authenticated it in his analysis of Musnad Ahmad (10/78).
❖ Abu Hurayrah, Allah be pleased with him, said: “The Messenger of Allah ﷺ said: ‘Allah approves three things for you and disliked that you do three others: he approves for you worshipping Him without partners, that you unite upon His rope, and that you do not divide among yourselves. He dislikes for you tittle-tattle, abundantly asking the people, and wasting wealth.”  Reported by al-Bukhari (1477) and Muslim (1715) and this is his wording. Quotes of the Predecessors and Scholars on Dispraising Extravagance and Wastefulness
❖ `Umar, Allah be pleased with him, said: “It is sufficient as extravagance for a person that he eats whatever he desires.”  al-Haytami mentioned it in al-Sawa`iq al-Muhriqah (1/298).
❖ Ibn `Abbas, Allah be pleased with them both, said: “Eat what you wish and dress in what you wish so long as two qualities are absent from you: extravagance and arrogance.”  Reported by Ibn Abi Shaybah in al-Musannaf (24878).
❖ `Uthman ibn al-Aswad said: “I was circumambulating the House with Mujahid, and he said: ‘If one spends one-thousand dirhams for the sake of Allah, one would not be extravagant. Yet, if one spent a single dirham in disobeying Him, he is extravagant.’”  Tafsir al-Qur’an, Abu Muzaffir al-Sam`ani (3/235). Forms of Extravagance and its Manifestations
Extravagance with the self in sins and wrongdoing. Allah, exalted, says: “Say, ‘My slaves who have harmed yourselves by your own excess, do not despair of Allah’s mercy. Allah forgives all sins: He is truly the Most Forgiving, the Most Merciful.” al-Zumar: 53. Extravagance in eating and satiating oneself excessively. Excessiveness in ablution. Excessiveness in public water facilities. Harms of Extravagance and Wastefulness
Allah does not love the extravagant and wasteful. Allah, exalted, says: “Do not waste. Surely, He does not like the wasteful.” al-An`am: 141. It leads to one seeking wealth in unlawful means. A prodigal person may find himself financially constrained, so to maintain his lifestyle he seeks impermissible wealth to satiate his desire. Extravagant eating harms the body. The devil is an associate to he who is extravagant and wasteful. Extravagance and wastefulness are among the attributes of the brothers of the devil. Extravagance leads to many blameworthy deeds. The extravagant will be accountable for his wealth and what he spent it on. Means to Desisting from Extravagance and Wastefulness
Moderation in expenditure. Distancing oneself from the extravagant and wasteful. Reading the biography of the Prophet ﷺ and the Righteous Predecessors. Contemplating the consequences of extravagance and wastefulness. If one realises their evil, he would avoid them. Mindfulness of death and the Final Abode. It is among the best ways to avoid extravagance, seeking proximity to Allah by giving excess to charity. Reasons for Extravagance and Wastefulness
Ignorance of the Law’s rulings, and that extravagance is forbidden. Being influenced by one’s environment. If one lives in an environment where it is the norm, it is likely he will imitate his folk. Relief after constraint. There is a type of people who find it difficult to stand on middle ground, going from one extreme to another.  Afat `ala al-Tariq, al-Sayyid Muhammad Nuh. Heedlessness of the next life. Accompanying the extravagant and the wasteful. The Messenger of Allah ﷺ said: “Man is upon the way of his intimate friend. Let each of you consider whom they take as intimate friends.”  Reported by Abu Dawud (4833), al-Tirmidhi (2378), and Ahmad (8317) and this is his wording, from the narration of Abu Hurayrah, Allah be pleased with him. al-Tirmidhi said: “It is sound, strange.” al-Nawawi authenticated its chain in Riyad al-Salihin (177). Ibn Hajar graded it as sound in al-Amali al-Mutlaqah (151).