1. A Muslim should not deal with interest.
Allah says in Glorious Quran:
"Those who devour usury will not stand....Allah has permitted trade and forbidden usury.... Allah will deprive usury of all blessing but will give increase for deeds of charity..." (2:275-6)
"O you who believe! Devour not usury, doubled and multiplied. But fear Allah, that you may really prosper" (3:130)
These aayat clearly indicate the seriousness of prohibition of usury and all interest-based transactions. It is not permissible for a Muslim to give or take interest whether from Muslim or from nonmuslim.
It is reported that theProphet Muhammad (peace be upon him) cursed those who pay interest, those who receive it, those who write a contract based on it, and those who witness such a contract.
2. Avoid deceit and fraud.
It is forbidden to gain property or wealth by fraud, deceit, theft, or other falsehoods. "
Give just measure and weight, and do not withhold from people the things that are their due. And do not do mischief on the earth after it has been set in order. That will be best for you if you have faith" (7:85).
Gaining property by means of frauds and deceit are evil actions and there is for them the severe punishment, in this world and in the hereafter.
3. The Haraam earnings.
The things from which earnings are forbidden include gambling, lotteries, buying and selling alcohol and other forbidden or haraam things.
"O you who believe! Intoxicants and gambling, sacrificing to stones, and divination by arrows are an abomination of Satan's handiwork. Eschew such abomination, that you may prosper" (5:90).
4. The hoarding is unlawful.
It is unlawful to hoard food and other basic necessities.
Everyone should take what they need and no more.
"And let those who covetously withhold of the gifts which Allah has given them of His Grace think that it is good for them. No, it will be the worse for them. Soon it will tie to their necks like a twisted collar, on the Day of Judgment. To Allah belongs the heritage of the heavens and the earth, and Allah is well-acquainted with all that you do" (Qur'an 3:180).
5. No extravagance and wastage.
A Muslim should be responsible in spending money.
Extravagance and waste are strongly discouraged. "[The Servants of Allah are] Those who, when they spend, are not extravagant and not stingy, but hold a just balance between those extremes" (Qur'an 25:67). "O Children of Adam! Wear your beautiful apparel at every time and place of prayer. Eat and drink, but waste not by excess, for Allah loves not the wasters" (7:31).
6. Give in charity.
Muslims must pay Zakat (alms).
"And they have been commanded no more than this: to worship Allah, offering Him sincere devotion, being true in faith. To establish regular prayer, and to give zakat. And that is the religion right and straight" (98:5).
A Muslim who owns certain wealth, more than the amount that meets his needs must pay a fixed rate of zakat to those in need. It is a means by which the sins are expiated, the division between rich and poor is narrowed and the needs of needy are fulfilled. It means that no one may sleep hungry.
Muslims are encouraged to give constantly in charity.
"Your riches and your children may be but a trial. Whereas Allah, with Him, is the highest reward. So fear Allah as much as you can, listen and obey, and spend in charity for the benefit of your own souls. And those saved from the selfishness of their own souls, they are the ones that achieve prosperity" (64:15-16).
The Prophet Muhammad once said that "nobody's assets are reduced by charity."