You should refer him to the work Raf‘ al-‘Itab wa l-Malam ‘amman qala l-‘Amal bi l-Da‘if Ikhtiyaran Haram by Shaykh Muhammad Qasim al-Qadiri al-Hasani al-Maghribi al-Fasi (available here) which proves conclusively that in the Maliki madhhab one must follow the mashhur and rajih - and the rajih when they conflict. See also here.
Originally Posted by ImamGhazzaali
Shaykh al-Fasi quotes al-Wanshirisi who said: "As for acting on or issuing fatwa on or decreeing by [shadhdh] opinions or [weak] views without deliberating on the rajih and without following the mashhur and the sahih, it is not permissible and is not allowed, and if he does so, he has sinned, without disagreement, and is ignorant and has gone against the path of ijma‘." (quoted on page 11)
Here are translations of excerpts from the first three chapters of Shaykh al-Fasi's work which should clarify a few issues:
When I came across the clear statements of the luminous guided imams and the great noble masters on the issue of what a person acts upon for himself – and draws near to Allah Almighty thereby... – and I found them stating that acting on the mashhur and the rajih is obligatory (wajib) in preference; and that acting on its opposite is haram except in dire need; I wanted – seeking help from the power of Allah and His strength, and depending on His will and support – to explain what I came across of those texts so the lay and elite can benefit from them – by the grace of Allah – along with simple words on what muftis issue fatwa on and judges issue decrees upon; and I will add to that – with the power of Allah and His strength – whatever our Master, the Knower, the Owner, makes easy.
Know that I restricted this book – asking Allah Almighty for practice upon knowledge – to an introduction and ten chapters and a conclusion. In the introduction is mentioned ten questions with their general answers, and in the ten chapters are mentioned the evidences of those answers...
Know that here are ten questions and ten answers:
1. Are the mashhur and rajih same or are they different? Answer: Upon verification, they are different.
2. When the mashhur and rajih contradict, is the mashhur given preference in terms of practice, fatwa and decree, or the rajih? Answer: The rajih is given preference.
3. Is it obligatory (wajib) for a person – in his own practice or a fatwa for another or a judicial decree on another – to adopt the mashhur or rajih or is it preferred? Answer: The truth is that it is wajib.
4. Is practice, fatwa and decree upon a weak opinion without dire necessity haram or not? Answer: It is haram.
5. When the common people act on a weak opinion as preference again and again until it becomes a norm and habit for them, is it haram for a person to follow them in doing what they do or not? Answer: It is haram for him to follow them.
Chapter One: On the Evidence that the Mashhur and the Rajih are Different upon Verification
Know that there are three different views on the reality of mashhur:
1. This is the correct view, that it is what was adopted by many. Al-Wanshirisi said in al-Mi‘yar: “According to this opinion on the meaning of mashhur, it is necessary for it to have more than three [scholars] who adopted it,” meaning: It is not said about a ruling that it is mashhur unless more than three scholars have adopted it.
2. That which is strong in evidence.
3. It is the statement of Ibn al-Qasim in al-Mudawwanah.
We only said the first is correct because ‘Allamah al-Hilali opened with it in his commentary on the khutbah of al-Mukhtasar, and he supported it with three matters:
1. This meaning accords with the linguistic meaning of the word mashhur because shuhrah linguistically is – as will come shortly – the appearance of something, and there is no doubt that a ruling that is issued by a group more than three is apparent/manifest.
2. It is the madhhab of the fuqaha’ and usuliyyun to give preference to the rajih over the mashhur when they contradict, and if we did not interpret mashhur to mean that which was adopted by many and instead interpreted it to mean that which is strong in evidence, it would be synonymous with rajih, so there will be no opportunity for contradiction between them such that it can be said rajih is given preference over it. [Therefore number 2 is ruled out]
3. The scholars mentioned that one of two opinions can be mashhur due to the abundance of those who adopted it and rajih due to the strength of its evidence.
(End approximate quote)
An example of this is listening to musical instruments, as it is haram according to the mashhur due to the number of those who ruled that it is prohibited exceeding three, and likewise it is haram according to the rajih because of the strength of the evidence, which is his (Allah bless him and grant him peace) statement as in the Sahih [of Imam al-Bukhari]: “There will be amongst my ummah groups that seek to make permissible private parts, silk, wine and musical instruments.”
Thus if mashhur was [by definition] that which is strong in evidence it would not arise in a single issue that it is mashhur or rajih by two different considerations.
Hence, these three matters support the meaning of mashhur that it is what was adopted by many, and refute those who interpret it as that which is strong in evidence.
As for those who interpret it as the statement of Ibn al-Qasim in al-Mudawwanah, then his interpretation is rejected as said by al-Hilali in the aforementioned commentary, because there is no meaning to restricting the mashhur to what he mentioned because this was not said by anyone. And then he answered on their behalf that perhaps the intent of this speaker [who said mashhur is the statement of Ibn al-Qasim] is that the statement of Ibn al-Qasim in al-Mudawwanah is one category from the categories of mashhur, so this speaker is indicating that the intent of the abundance of those who adopted a view in their famous statement “that which is adopted by many” is the abundance of those who adopted it either in actuality or in outcome; because Ibn al-Qasim, although externally he is one, but because of his constant companionship with Malik for more than twenty years and he did not part from him until he died and because the Mudawwanah was narrated from him, he is more than three in outcome. This answer offered by al-Hilali is stipulated....
This is what relates to mashhur. As for rajih, there are two opinions about it. The correct of them is that which is strong in evidence. It was said: that which was adopted by many.
Know that the disagreement that has occurred in the word mashhur occurs in words that have the same meaning like their statement: “the majority (jumhur) is on this,” and their statement: “the madhhab of most (al-akthar) is such” and like their statement: “the madhhab is such” because the fuqaha’ often use the word madhhab for the opinion of most scholars of the madhhab not for the opinion of all the scholars of the madhhab, as evidenced by their mention of a text which they state is the madhhab and then mention of its opposite. This usage – that is their usage of the word madhhab for the majority – is a majaz mursal (metaphor) because it is using the word madhhab – that was originally designated for all of them – for most of them so it is like using the whole for its greater part as comes in the hadith “Hajj is ‘Arafah.” And often they use the word madhhab for the agreed-upon, in which case it is literal.
That which we mentioned – i.e. that which gives the meaning of mashhur is like stating it explicitly – was said by al-Hattab...
Moreover, the opposite of mashhur is called shadhdh. Thus, shadhdh is the opinion that was not issued by a group. And likewise the opposite of rajih is called weak. Thus, “weak” is that which does not have a strong evidence in that it is opposed by that which is stronger in evidence. Thus, its weakness is relative, meaning, it is weak in relation to what is stronger than it, even if it has strength in itself. Or it opposes consensus or the principles or an explicit text or manifest analogy, so it is weak in itself. This second type of weak is called weak of source (da‘if al-mudrak).
Furthermore, that which we mentioned of the interpretation of mashhur, rajih, da‘if and shadhdh, in what has preceded, that is what was transmitted from the fuqaha’, and that accords with the linguistic meaning of them. Thus in al-Qamus it states: “Shuhrah with damm is the appearance of a thing in notoriety i.e. publicity.” And in al-Misbah: “I made something rajih, by making it weighty: I made it preferred and I strengthened it.” And in al-Misbah it states: “Da‘f with fath of the dad in the language of Tamim and with damm in the language of Quraysh is the opposite of strength and soundness.” And in al-Qamus: “Shadhdha, yashudhdhu, and yashudhdhu, shadhdhan and shudhudhan: it was rare from what is common.” And in al-Mukhtar: “It became shadhdh from it: isolated from the majority.”
Moreover, often shadhdh is used in opposition to both mashhur and rajih, and da‘if likewise.
This is the last of what relates to the first chapter.
Chapter Two: On the Evidence of Giving Preference to the Rajih over the Mashhur when they Conflict
Know that giving preference to the rajih over the mashhur when they conflict is the position of the majority of the fuqaha’ and usuliyyin as has preceded from al-Hilali. And from those who stated this explicitly are ‘Izz al-Din ibn ‘Abd al-Salam al-Shafi‘i in his Qawa‘id and his student al-Qarafi [al-Maliki] in his summation of the Qawa‘id of his aforementioned teacher. My master, ‘Ali al-Jawhari, gave preference to it. And this is understood from the speech of Ibn Habib, Ibn al-‘Arabi and Ibn ‘Abd al-Barr, since they gave preference with respect to the recitation in the two rak‘ahs of [the sunnah of] Fajr that which is in Sahih Muslim from the hadith of Abu Hurayrah (Allah be pleased with him) that the Messenger of Allah (Allah bless him and grant him peace) would recite in Fajr: Qul Ya Ayyuha l-Kafirun and Qul Huwa Llahu Ahad due to its strength, although it is shadhdh according to the earlier scholars according to the mashhur, of sufficing with Fatihah in them, taken from the hadith of ‘A’ishah (Allah be pleased with her) that the Messenger of Allah (Allah bless him and grant him peace) would make the recitation light due to the weakness of this evidence as stated by the later scholars; and they explained this weakness by saying that lightening the recitation does not prove omitting a surah in them.
If you say: What you mentioned of giving preference to the rajih over the mashhur is contrary to what is in al-Zurqani in his statement on dalk (rubbing) in the bath of major ritual impurity, because it indicates that the mashhur is given priority over the rajih in opposition to what you said because the upshot of his statement there is that when there is a mashhur accepted by the majority, it cannot be rejected, even if its source is weak in our minds and the source of its opposite is strong; and its commentators, Bannani and Rahuni accepted his statement.
I say: There is no conflict at all due to the difference in subject-matter, because the subject-matter of giving preference to the rajih over the mashhur is when the mashhur has a weak source with certainty, in that all who spoke of it from the late scholars said it has a weak source, like sufficing in the two rak‘ahs of Fajr with Fatihah, because all who spoke on it from the late scholars said its evidence is weak. And the subject-matter of what al-Zurqani mentioned of giving preference to the mashhur over the rajih is when the weakness of the evidence of the mashhur is speculative only. And the example of this is dalk in the bath of major ritual impurity because the mashhur in this is that it is wajib in itself and its opposite is that it is wajib to make the water reach the skin; so the mashhur was given preference even if we think the evidence is weak...because when we think carefully we would say that those who adopted this opinion are not so many but because it has a strong evidence which we did not comprehend...so it will be both mashhur and rajih. This harmonisation is derived – upon consideration – from the speech of al-Zurqani in the discussion on the issue of dalk. And Allah knows best.
Chapter Three: On the Evidence of Acting on the Mashhur or the Rajih being Wajib just as Fatwa and Decreeing by Them is Wajib
Know that a group of righteous scholars and firmly-grounded fuqaha’ have stated explicitly that this is wajib. From them: Imam Malik, Ibn al-Qasim, ‘Isa ibn Dinar and Ibn Muzayyin, as al-Wanshirisi transmitted from them in al-Mi‘yar and his text is: “How brilliant is what Ibn Muzayyin narrated from ‘Isa ibn Dinar from Ibn al-Qasim from Malik that he said: “Not every statement said by a man is to be followed even if he has excellence, due to His (Exalted is He) statement: “Those who hear the word and follow the best of it.””” And the meaning of the aforementioned statement of Malik is that not every statement that issues from a learned scholar is taken into consideration and is counted, rather only an opinion that has a share in nazr [i.e. deliberation of the mashhur and rajih] is taken into consideration, and that is the mashhur or the rajih. And may Allah bless the one who said:
Not every disagreement that has come is regarded
Except a disagreement that has a share in deliberation [i.e. of what is mashhur and rajih]
And from them is Ibn Abi Jamrah and his teachers, and his statement is: “Those who we met of eminent scholars would say: It is not permissible for anyone to accept anything besides the mashhur and he cannot give fatwa except in accordance with it.” The teacher of teachers Abu al-Su‘ud Sayyidi ‘Abd al-Qadir al-Fasi transmitted it from him in his Nawazil.
From them is al-Qadi Abu Salim al-Yaznasini...
From them is ‘Allamah al-Wanshirisi as he said in al-Mi‘yar: “As for acting on or issuing fatwa on or decreeing by [shadhdh] opinions or [weak] views without deliberating on the rajih and without following the mashhur and the sahih, it is not permissible and is not allowed, and if he does so, he has sinned, without disagreement, and is ignorant and has gone against the path of ijma‘.”...
From them is al-Wali al-Salih, the teacher of teachers, Abu l-Barakat Sayyidi ‘Abd al-Qadir al-Fasi – may Allah illuminate by his stature our hard heart. He stated this in an answer of his recorded in his Nawazil where he said: “Acting on the mashhur is wajib, but adopting a weak opinion (lit: concession) for a particular period due to dire necessity is permissible.”
From them is al-Muhaqqiq al-Mutqin al-Shaykh Ibn ‘Arafah....
From them is al-Wali al-Salih Sayyidi ‘Abd al-Rahman al-Fasi...
From them is Shaykh Bannani...
From them is Wali al-Salih Sayyidi al-Tawidi ibn Sawdah...
From them is ‘Allamah al-Sa‘idi...
From them is Shaykh Imam Abu ‘Abd Allah Sayyidi Muhammad ‘Ulaysh...