The statement “the layman has no madhhab” (al-‘āmmī lā madhhaba lahū) was mentioned by some scholars. This rule applies only to the situation before the codification of madhhabs, as expressed by al-Juwaynī amongst others.
Nāsir al-Dīn Abu l-‘Abbās Ahmad ibn Muhammad Ibn al-Munayyir al-Mālikī (620 – 683 H) said:
“Proof dictates [the necessity of] adherence to a specific madhhab after [the codification of the madhhabs of] the four Imāms not before them. The difference is that the people before the four Imāms did not codify their madhabs, nor did the legal cases arise in large numbers upon them, such that the madhhab of each of them may be known in all cases or in most of them. The one who asks fatwa of al-Shāfi‘ī, for example, had no knowledge of what the mufti will say because his madhhab was not well-known in that case, or it did not arise before that so it is inconceivable that [anyone] supported it besides the mind of a specific [mufti].
As for after the madhhabs were understood, codified and became famous, and the dispensation was known from the strictures in every case, then a questioner will not alternate – when the condition is such – from madhhab to madhhab except due to an inclination to break away [from responsibility] and seeking ease.”
In this very clear passage, Ibn al-Munayyir explains that before the codification of madhhabs there was little scope to seek out the easiest opinions of the scholars. However, after the codification of the madhhabs, it would be easy to find the easiest opinion on each issue. Thus, at this time, restricting oneself to a single madhhab became necessary, as a regulatory measure. Hence, the rule, “The layperson has no madhhab” is applicable to the period before the codification of madhhabs.
Stating this explicitly, Ibn Hajar al-Haytamī from the late Shāfi‘ī school said:
“The claim that the layperson has no madhhab is rejected. Rather, taqlīd of a recognised madhhab is necessary for him. That [i.e. the layperson having no madhhab] was before the codification of madhhabs and their settlement.”
The rule “the layperson has no madhhab” also applies to those situations, times and places where it would be very difficult or even impossible to obligate a layperson to adhere to a single madhhab, due to complete ignorance or lack of access to all the positions of one madhhab. Some of the later scholars have mentioned this.
However, in normal circumstances, due to the reasons that have been explained, a layperson must adhere to a single madhhab in all its rulings.