Ruling 6

If the most learned mujtahid gives a fatwa on any matter, a follower (muqallid) of his cannot act upon another mujtahid’s fatwa in that matter.

However, if he does not give a fatwa and says that based on precaution, such and such action must be taken – for example, he says: ‘Based on precaution, in the first and second units (rakʿah) of a prayer, a complete chapter (surah) of the Qur’an must be recited after Sūrat al-Ḥamd’ – then the follower must either act according to this precaution, which is known as ‘obligatory precaution’ (al‐iḥtiyāṭ al‐wājib) or ‘necessary precaution’ (al-iḥtiyāṭ al-lāzim)³ or he must act according to the fatwa of the next most learned mujtahid;⁴ and if the next most learned mujtahid regards the recitation of only Sūrat al-Ḥamd as being sufficient, he can choose not to recite the other surah.

The same applies [i.e. it amounts to saying the ruling is based on obligatory precaution] when the most learned mujtahid says the matter is one of ‘deliberation’ (maḥall al‐taʾammul) or ‘problematic’ (maḥall al‐ishkāl).

^3. To avoid over-complicating the text, and given that ‘al‐iḥtiyāṭ al‐wājib’ and ‘al-iḥtiyāṭ al-lāzim’ refer to the same thing, both terms have been translated in the present work as ‘obligatory precaution’.
^4. In the terminology of Islamic jurisprudence, acting on the fatwa of the next most learned mujtahid when one’s marjaʿ has stated that a ruling is based on obligatory precaution is known as ‘rujūʿ’.