Tafsir of Al-Isra 17:27

إن المبذرين كانوا إخوان الشياطين

Verily, the spendthrifts are brothers of the Shayatin, They have this trait in common. Ibn Mas`ud said: "This refers spending extravagantly when it is not appropriate.'' Ibn Abbas said likewise. Mujahid said: "If a man spends all his wealth on appropriate things, then he is not a spendthrift, but if he spends a little inappropriately, then he is a spendthrift.'' Qatadah said: "Extravagance means spending money on sin in disobeying Allah, and on wrongful and corrupt things.'' Imam Ahmad recorded that Anas bin Malik said: "A man came from Banu Tamim to the Messenger of Allah and said: `O Messenger of Allah, I have a lot of wealth, I have a family, children, and the refinements of city life, so tell me how I should spend and what I should do.' The Messenger of Allah said:

تخرج الزكاة من مالك إن كان فٳنها طهرة تطهرك

وتصل أقرباءك

وتعرف حق السايل والجار والمسكين

Pay the Zakah on your wealth if any is due, for it is purification that will make you pure, maintain your ties of kinship, pay attention to the rights of beggars, neighbors and the poor. He said: `O Messenger of Allah, make it less for me.' He (recited):

وآت ذا القربى حقه والمسكين وابن السبيل وﻻ تبذر تبذيرا

And give to the kinsman his due, and to the Miskin (poor) and to the wayfarer. But spend not wastefully in the manner of a spendthrift. The man said, `That is enough for me, O Messenger of Allah. If I pay Zakah to your messenger, will I be absolved of that duty before Allah and His Messenger!' The Messenger of Allah said:

نعم إذا أديتها إلى رسولي فقد بريت منها ولك أجرها وإثمها على من بدلها

Yes, if you give it to my messenger, you will have fulfilled it, and you will have the reward for it, and the sin is on the one who changes it.''

إن المبذرين كانوا إخوان الشياطين

Verily, the spendthrifts are brothers of the Shayatin, meaning, they are their brothers in extravagance, foolishness, failing to obey Allah and committing sin. Allah said:

وكان الشيطان لربه كفورا

and the Shaytan is ever ungrateful to his Lord. meaning, he is an ingrate, because he denied the blessings of Allah and did not obey Him, turning instead to disobedience and rebellion