Imam Sadiq (Pbuh) has said the following in interpretation...

Imam Sadiq (Pbuh) has said the following in interpretation of a verse in the Quranic chapter Baqara. "Our Lord! Give us good in this world and good in the Hereafter..." (verse 201) The good in the Hereafter is God's Pleasure and Heaven, and the good in this life is a good temper and bountiful daily bread. [Bihar al-Anwar , v.71, p.383] Thus, we can conclude that the believers wealth and property are similar to a factory in which God's Pleasure and a musk-scented Heaven are produced.

Believers earn their income through legitimate business transactions, abiding by the law and avoiding unlawful transactions. In short, they earn money through continuous lawful transactions and by obeying God. They spend their income for the expenses of their household, paying the alms-tax and the one-fifth levy. They spend the rest to help the deprived, the oppressed, the weak and to aid relatives and friends.

Spending legitimately earned income in these ways is natural and lawful and is in fact considered to be worship and obedience: Or as the Holy Quran has said - It is the good of this world and the Hereafter. It is for this reason that wealth and property has been interpreted to be good and blessed in God's Book. Earning and spending it is considered to be worship for the believers and a cause of great reward and infinite divine gifts.

It is interesting to hear the viewpoint of the Commander of the Faithful (Imam Ali) about wealth in the hands of irreligious, lustful people: Property is the material of lust, is subject to catastrophes, strengthens aspirations and entertains the inheritors. Wealth will raise the status of the owner in this world and lower it in the Hereafter. [Mizan al-Hikmat , v.9, pp.277-78] The Prophet (Pbuh) said: Gold and silver destroyed those before you and will destroy you, too.

[Ibid] He also said: For each nation there is a calf and for this nation the calf is silver and gold. [Ibid] (the calf refers to the golden calf idol made by the Israelites). Truly, wealth enslaves those of weak faith with illegitimate lusts and excitement of their aspirations. They become base in this world and in the Hereafter, and as the Prophet of Islam (Pbuh) has commented: people began to worship the calf in the form of the worship of wealth.

The Forbidden and the Unforbidden Undoubtedly, whatever a person earns from working and from his business affairs is lawful.