He , the Sublime and Exalted, says:
“But spend not wastefully ( your wealth) in the manner of a spendthrift” (al-Isra` 17:26 )
He, the Sublime, warns from at-Tabdheer which is spending wealth on unlawful things.
For example, spending wealth to oppress people or harm them, or spending it on oppressing one’s self such as spending it on intoxicants, narcotics, cigarettes, fornication and adultery, and the rest of the acts of disobedience, such as gambling and games of chance and the likes.
Also is the ruling of destroying it wealth without right such as excessive spending and purchasing products of which you have no need . this is from wasting wealth and from at-Tabdheer, and the Messenger (صلى الله عليه وسلم ) has forbade wasting money.
Thus, at-Tabdheer is spending wealth in its incorrect ways, either acts of disobedience or on that which contains no benefit, out of play or neglecting money.
As for al-Israaf then it is the excess, un-necessary spending.
For example: a person eats and drinks extra food and drinks without need, such as if a kilo of food or a kilo of meat is enough for him but he adds more food or meat that he is not in need of. Consequently, the leftover food is thrown in the dirt or in the garbage; this is called Israaf.
Destroying wealth without a just cause and wasting it is also called Tabdheer, He, the Sublime, has clarified that those who make Tabdheer are brothers of the devils because they inmate them in play, wasting and disobedience.
Said Imaam ‘Abdul-‘Azeez Ibn ‘Abillah Ibn Baaz :
”Allah, the sublime and exalted, has sent down in His Grand Book many aayaat where wasting and extravagance is mentioned along with the prohibition of both, and the praise of those who adopt the middle course, and are moderate and Upright in their actions, eating, drinking and the rest of their spending. Therefore, there shouldn’t be any wastefulness, extravagance, miserliness, niggardliness, extremism, or negligence.”
Thusly Allah has ordained for the middle course to be adopted in all affairs oand from this is the prohibition of extremism.
Source : Taken from “A Warning from Wastefulness and Extravagance” by Ibn Baaz