Ijtihād is the third source from which the laws of Islām are drawn. The word itself is derived from the root jahd which means exerting oneself to the utmost or to the best of one’s ability, and Ijtihād, which literally conveys the same significance, is technically applicable to a lawyer’s exerting the faculties of mind to the utmost for the purpose of forming an opinion in a case of law respecting a doubtful and difficult point (LL.)
Reasoning or the exercise of judgment, in theological as well as in legal matters, plays a very important part in the religion of Islām, and the value of reason is expressly recognized in the Holy Qur’ān, which is full of exhortations like the following: “Do you not reflect?” “Do you not understand?” “Have you no sense?” “There are signs in this for a people who reflect;” “There are signs in this for a people who understand;” and so on. Those who do not use their reasoning faculty are compared to animals, and spoken of as being deaf, dumb and blind:
“And the parable of those who disbelieve is as the parable of one who calls out to that which hears no more than a call and a cry. Deaf, dumb, blind, so they have no sense” (2:171).
“They have hearts wherewith they understand not, and they have eyes wherewith they see not, and they have ears wherewith they hear not. They are as cattle; nay, there are more astray” (7:179).
“The vilest of beasts in Allāh’s sight are the deaf, the dumb, who understand not” (8:22). “Or thinkest thou that most of them hear or understand? They are but as the cattle; nay, they are farther astray from the path” (25:44).
While those who do not exercise their reason or judgment are condemned, those who do it are praised: