Al-Hashr (The Gathering) Sura 59: Verse 7 (partial)
"Whatever gains God turns over to His Messenger from the people of the townships belong to God, the Messenger, kinsfolk, orphans, the needy and the traveller in need. Thus, they would not just circulate among those of you who are rich."
This verse states a major rule of the Muslim community's economic and social system: thus, money "would not just circulate among those of you who are rich." Although the rule is stated in connection with the gains made in a particular encounter, the rule goes beyond the immediate event to state fundamental principle for the Islamic social system.
Islamic economic system approves private ownership but makes it subject to this rule that excludes the possibility of wealth being circulated only among the rich in society. Whatever situation leads to the poor being outside the general circulation of wealth, keeping it only in the hands of the rich, is contrary to the Islamic economic system and works against one of its major social organization objectives. All transactions in the Muslim community must be so organized so as not to allow such a situation to develop, and to dismantle it if it does exist. Thus, Islamic system makes Zakat an essential duty. The system Islam approves of for renting agricultural land is based on sharing the produce between the owner and the renter. Islam strictly forbids monopoly and usury, which are the two main tools that lead to money being circulated purely among the rich. This shows that the whole economic system Islam lays down is geared to implementing this most important rule.