Maslahah literally means benefit or interest. When qualified as Maslahah Mursalah it refers to unrestricted public interest. Maslahah Mursalah is synonymous with Istislah which is also called Maslahah Mutlaqah.
Al Ghazali thinks Maslahah consists of considerations which secure a benefit or prevent a harm. Protection of life, religion, intellect, lineage and property is Maslahah.
On the basis of Maslahah, the companions decided to issue currency, to establish prisons and impose Kharaj (agricultural land tax). The Ulama of Usul are in agreement that Istislah is not a proof in respect of devotional matters (Ibadah) and in respect of specific Shariah injunctions like shares of inheritance. The majority of Ulama maintain that Istislah is a proper ground for legislation.
Al-Shatibi points out that this is the purpose of Quranic Ayat No. 107 of sura Al Anbiya that "We have not sent you but as a mercy for all creatures". There is support for Maslahah in the Quran in Sura Younus (10:7), in Sura Hajj (22:78) and in Sura Al-Maidah (5:6).
The Ulama have quoted a number of Hadith in support, such as the following :
"The Prophet only chose the easier of two alternatives so long as it did not amount to a sin".
"Allah loves to see that His concessions (rukksah) are observed, just as He loves to see that His strict laws (azaa-im) are observed".
The above would confirm that no unnecessary rigour is recommended in the enforcement of Ahkam and that the Muslims should avail of the flexibility and concessions of Shariah.
All the Khulafa-I-Rashidun acted in pursuance of Maslahah. Abu Bakr compiled the Quran. Umar held his officials responsible for abuse of public office. Uthman distributed the authenticated copy of the Quran and destroyed the copies of variant texts. Ali held the craftsmen and traders responsible for the loss of goods that were placed in their custody.
Maslahah has been upheld by the majority of Ulama. However, strong support for it comes from Imam Malik. Maslahah has been divided into three types by Shatibi and some other scholars -
the complementary [hajjiyat] and
From the point of view of availability or otherwise of textual authority, Maslahah has been further sub-divided into the following :
al-Maslahah al-Mutabarah [accredited Maslahah] which has been upheld in the Shariah such as defending the right ownership by penalizing the thief.
Maslahah Mursalah is that which has neither been upheld nor nullified by the Shariah such as provision in law in many Muslim countries for documentary evidence to prove marriage or ownership of property.
Maslahah Mulgha which has been nullified either explicitly or by indications in Shariah.
To validate Maslahah the following conditions have to be met :
Maslahah must be genuine,
Maslahah must be general (Kulliyah) - that is it secures Maslahah for all.
it must not be in conflict with clear Nass.
As regards relation among Qiyas,- Istihsan and Istislah, - it may be stated that Qiyas and Istihsan are essentially based on Illah in the Nasus (hidden or obvious).
Law is expanded by Qiyas or Istihsan on the basis of Illah of Nasus. But when law can not be made on the basis of Nasus or through Qiyas and Istihsan, law is made on the basis of Maslahah or public interest.