Al-Maslahah linguistically: It is taken from the verb or from and it is the opposite of n meaning (which means: to ruin/corrupt) Its meaning is therefore to rectify, make better or right.

Al-Maslahah carries the meaning of As-Salaah (properness/intactness) and the meaning of Al-Manfa’ah (benefit/interest/advantage). The plural of Maslahah is Masaalih.

Al-Mursal: The unrestricted (Mutlaq) without a Qaid (restriction/limitation) or it means a Daleel

It is an expression of the Wasf (description) that appears to the Mujtahid to be most likely to bring the Maslahah (benefit/interest) or repel the Madarrah (harm/detriment) when building the Hukm upon that Wasf (description) without the Mujtahid finding from the Shaari’ (Legislator) that which indicates the cancellation of this Wasf (description) or reliance in it.

Said differently: It represents the Amr ul-Munaasib (suitable or fitting matter) for the legislation of the Ahkaam in respect to the incidents and realities in which there is no Hukm for them to the Shaari’ (legislator), based upon the angle of acquiring a benefit or repelling a Mafsadah (cause of corruption or something bad).

Al-Ghazaaliy called Al-Maslahah Al-Mursalah: Al-Istislaah

As for Imaam Al-Haramaini (Al-Juwainiy) and Ibn As-Sam’aaniy then they called it: Istidlaal.

The Maslahah has been called a Maslahah because building the Hukm upon it is thought (most likely) to lead to the acquisition of benefits or to repel harms or negative bad things (Mafaasid). It has been described as Mursalah due to it being free or empty of a Daleel Shar’iy in respect to its consideration or its cancellation from the Shar’i perspective.

The ‘Ulamaa have agreed upon the impossibility of working with Al-Masaalih Al-Mursalah in a matter from the matters of the ‘Ibaadaat (acts of worship) because they have come Tawqeefiy (as they are and without reasoning) from Allah Ta’Aalaa, and defined and specified by the Shar’iyah texts from the Kitaab and the Sunnah. This is like the Salaah, the Sawm, Hajj and Zakaah, including the manner of how to perform or undertake these acts. It is therefore obligatory upon the Muslims to abide by them in accordance to that which has been explained to them in terms of the Ahkaam. This applies to the Hudood, Kaffaaraat (acts of expiation), ‘Ibaadaat and Meeraath (inheritance) and whether the angle of Maslahah appears to us or does not appear.

Example of Al-Maslahah Al-Mursalah:

When ‘Umar Ibn Al-Khattaab (ra) was the Khalifah he poured out (emptied) the milk that had been mixed with water to discipline those who were committing this fraud. This fits into the remit of the Maslahah so that they would not cheat the people in this way after that.

Another example:

The Sahaabah (ah) approved of the killing of the group or collective for the murder of one if they participated in his killing because the Maslahah dictated that. That is to prevent two or more to take part in the killing of a single person in an attempt to avoid the Qisaas (law of retribution). It is so that no one who brought in someone else to assist him in killing a person can be saved from Al-Qisaas and so that the blood of the victim does not flow in vain (i.e. without retribution) and Al-Qisaas is made redundant. It has been related that a group killed one person in Sana’a and so ‘Umar Ibn Al-Khattaab commanded that they all be killed. He (ra) said:

Had the people of Sana’a (as a whole) gathered upon it then I would have killed them for it