尽管哈乃斐学派等一些学者接受理性推断出的"Illah"（效因），但最有力的观点是，效因必须源自经文。这是因为，除非真主（subhanahu wa ta'ala）已经启示了律例的理由，理智本身无法确定这些理由。效因是将律例扩展到新事物的依据（daleel）。要使这一律例成为有效的沙里亚律令（Hukm Shar'i），即沙里亚的合法裁定，它必须取自立法者的言语（Khitaab），因为沙里亚律令的定义正是立法者关于人的行为的言语。任何不出自立法者言语的律例都会被拒绝，因为它不是启示（Wahiy），而我们只被命令在行为上遵循启示。若在没有经文效因的情况下扩展律例，就如同仅仅因为醋源自酒，便将禁酒的规定延伸到醋上。酒是一种事物，醋是另一种事物。人不能在经文未允许such扩展的情况下，任意扩展律令。如果经文通过某个效因允许了这种扩展，那么这就是有效的沙里亚律令；如果没有，那它只是一种理性判断，在沙里亚中没有价值。

Although some scholars like those from the Hanafi school accept rationale „Illah‟s, the strongest position is that the „Illah must be from the text. This is because the mind is not capable to determining the reasons for the rules unless they have been revealed by Allah (swt). The „Illah is the daleel which allowed the extension of the rule to a new matter. For this rule to be a Hukm Shar‟i i.e. a valid ruling of the Shar‟iah, it must be taken from the speech (Khitaab) of the Legislator since the definition of Hukm Shar‟i is the speech of the Legislator relating to man‟s actions. Any rule which is not from the speech of the legislator is rejected because it is not revelation (Wahiy) and we are ordered only to follow the Wahiy in our actions. To extend the rule without a textual „Illah would be like extending the prohibition of alcohol to vinegar just because vinegar originates from alcohol. Alcohol is one reality and vinegar is another. One cannot arbitrarily extend the Hukm without the text allowing such an extension. If the text allows it through an „Illah, then this is a valid Hukm Shar‟i, if not then it is a rational judgment which has no value in the Shar‟iah.