Mustalah al-Hadith mempunyai hubungan yang erat dengan Rijal al-Hadith (kajian tentang perawi hadith). Dalam meneliti perawi sesuatu hadith, kenyataan-kenyataan yang menguatkan atau mencela yang dibuat oleh pakar-pakar yang diiktiraf, daripada kalangan Tabi'in dan selepas mereka, didapati sangat membantu. Contoh kenyataan tersebut, mengikut susunan daripada yang paling kuat penilaiannya, ialah:

Mustalah al-Hadith is strongly associated with Rijal al-Hadith (the study of the reporters of hadith). In scrutinising the reporters of a hadith, authenticating or disparaging remarks made by recognised experts, from amongst the Successors and those after them, were found to be of great help. Examples of such remarks, in descending order of authentication, are:

"Imam (pemimpin), Hafiz (penghafaz)."

• "Imam (leader), Hafiz (preserver).".

"Boleh dipercayai, amanah."

• "Reliable, trustworthy.".

"Membuat kesalahan."

• "Makes mistakes.".

"Lemah."

• "Weak.".

"Ditinggalkan (oleh para ahli hadis)."

• "Abandoned (by the traditionists).".

"Pendusta, pernah mereka-reka hadith."5.

• "Liar, used to fabricate ahadith."5.

Perawi yang secara sebulat suara digambarkan dengan pernyataan seperti dua yang pertama dapat menyumbang kepada isnad yang sahih ("sahih", lihat kemudian). Isnad yang mengandungi perawi yang digambarkan dengan dua pernyataan terakhir kemungkinan besar adalah da'if jiddan (sangat lemah) atau maudu' (direka-reka). Perawi yang menjadi subjek pernyataan seperti dua yang di tengah di atas akan menyebabkan isnad itu da'if (lemah), walaupun beberapa perawi yang meriwayatkan hadith yang sama secara bebas sering kali akan menaikkan taraf hadith itu ke tahap hasan (baik). Jika kenyataan mengenai seseorang perawi itu bercanggah, satu keputusan yang teliti hendaklah dicapai selepas analisis mendalam, contohnya terhadap sebab yang diberikan bagi sebarang celaan, bobot setiap jenis kritikan, tahap ketegasan atau kelonggaran setiap pengkritik, dan sebagainya.

Reporters who have been unanimously described by statements such as the first two may contribute to a sahih ("sound", see later) isnad. An isnad containing a reporter who is described by the last two statements is likely to be da'if jiddan (very weak) or maudu' (fabricated). Reporters who are the subject of statements such as the middle two above will cause the isnad to be da'if (weak), although several of them relating the same hadith independently will often increase the rank of the hadith to the level of hasan (good). If the remarks about a particular reporter conflict, a careful verdict has to be arrived at after in-depth analysis of e.g. the reason given for any disparagement, the weight of each type of criticism, the relative strictness or leniency of each critic, etc.

Komentar-komentar terawal yang dinukilkan dalam kitab-kitab Rijal berasal daripada ramai tabi'in, diikuti oleh mereka yang datang selepas mereka sehingga zaman para ahli hadis yang enam, iaitu tempoh yang meliputi tiga kurun pertama Islam. Senarai nama-nama sedemikian disediakan oleh penulis dalam tesisnya, Criticism of Hadith among Muslims with reference to Sunan Ibn Majah, pada akhir bab IV, V dan VI. Antara karya terawal yang tersedia dalam bidang ini ialah Tarikh karangan Ibn Ma'in (w. 233), Tabaqat karangan Khalifa b. Khayyat (w. 240), Tarikh karangan al-Bukhari (w. 256), Kitab al-Jarh wa 'l-Ta'dil karangan Ibn Abi Hatim (w. 327) dan Tabaqat karangan Muhammad b. Sa'd (w. 320).

The earliest remarks cited in the books of Rijal go back to a host of Successors, followed by those after them until the period of the six canonical traditionists, a period covering the first three centuries of Islam. A list of such names is provided by the author in his thesis, Criticism of Hadith among Muslims with reference to Sunan Ibn Majah, at the end of chapters IV, V and VI. Among the earliest available works in this field are Tarikh of Ibn Ma'in (d. 233), Tabaqat of Khalifa b. Khayyat (d. 240), Tarikh of al- Bukhari (d. 256), Kitab al-Jarh wa 'l-Ta'dil of Ibn Abi Hatim (d. 327) and Tabaqat of Muhammad b. Sa'd (d. 320).

Sebilangan ahli hadis membuat usaha khusus untuk mengumpulkan maklumat tentang perawi-perawi bagi lima koleksi hadis yang terkenal, iaitu koleksi al-Bukhari (m. 256), Muslim (m. 261), Abu Dawud (m. 275), al-Tirmidhi (m. 279) dan al-Nasa'i (m. 303), dengan memberikan kenyataan pengesahan dan celaan secara terperinci. Karya utama pertama yang turut memasukkan perawi-perawi Ibn Majah (m. 273) ialah koleksi sepuluh jilid al-Hafiz 'Abd al-Ghani al-Maqdisi (m. 600), yang dikenali sebagai Al-Kamal fi Asma' al-Rijal. Kemudian, Jamal al-Din Abu 'l-Hajjaj Yusuf b. 'Abd al-Rahman al-Mizzi (m. 742) menyediakan versi yang disunting dan diringkaskan bagi karya ini, dengan disertakan penanda tempat dan negeri asal para perawi; beliau menamakannya Tahdhib al-Kamal fi Asma' al-Rijal dan menghasilkannya dalam dua belas jilid. Seterusnya, salah seorang murid al-Mizzi yang cemerlang, Shams al-Din Abu 'Abdullah Muhammad b. Ahmad b. 'Uthman b. Qa'imaz al-Dhahabi (m. 748), merumuskan karya syeikhnya dan menghasilkan dua ringkasan: yang lebih panjang dinamakan Tadhhib al-Tahdhib dan yang lebih pendek dinamakan Al-Kashif fi Asma' Rijal al-Kutub al-Sittah.

A number of traditionists made efforts specifically for the gathering of information about the reporters of the five famous collections of hadith, those of al-Bukhari (d. 256), Muslim (d. 261), Abu Dawud (d. 275), al- Tirmidhi (d. 279) and al-Nasa'i (d. 303), giving authenticating and disparaging remarks in detail. The first major such work to include also the reporters of Ibn Majah (d. 273) is the ten-volume collection of al-Hafiz 'Abd al-Ghani al-Maqdisi (d. 600), known as Al-Kamal fi Asma' al-Rijal. Later, Jamal al-Din Abu 'l-Hajjaj Yusuf b. 'Abd al-Rahman al-Mizzi (d. 742) prepared an edited and abridged version of this work, punctuated by places and countries of origin of the reporters; he named it Tahdhib al- Kamal fi Asma' al-Rijal and produced it in twelve volumes. Further, one of al-Mizzi's gifted pupils, Shams al-Din Abu 'Abdullah Muhammad b. Ahmad b. 'Uthman b. Qa'imaz al- Dhahabi (d. 748), summarised his shaikh's work and produced two abridgements: a longer one called Tadhhib al-Tahdhib and a shorter one called Al-Kashif fi Asma' Rijal al-Kutub al- Sittah.

Satu usaha yang serupa dengan karya al-Mizzi telah dilakukan oleh Ibn Hajar (w. 852H), yang menyediakan sebuah versi yang panjang tetapi diringkaskan, dengan kira-kira satu pertiga daripada karya asal dihilangkan, bertajuk Tahdhib al-Tahdhib dalam dua belas jilid yang lebih pendek. Kemudian, beliau meringkaskan lagi karya ini menjadi sebuah karya dua jilid yang agak sederhana bernama Taqrib al-Tahdhib.

A similar effort with the work of al-Mizzi was made by Ibn Hajar (d. 852), who prepared a lengthy but abridged version, with about one- third of the original omitted, entitled Tahdhib al-Tahdhib in twelve shorter volumes. Later, he abridged this further to a relatively-humble two- volume work called Taqrib al-Tahdhib.

Karya al-Dhahabi tidak dibiarkan tanpa suntingan; al-Khazraji (Safi al-Din Ahmad b. 'Abdullah, meninggal selepas 923) meringkaskannya dan turut membuat tambahan yang bernilai, lalu menghasilkan Khulasah beliau. Sejumlah karya yang serupa membincangkan sama ada perawi yang thiqah sahaja, contohnya Kitab al-Thiqat oleh al-'Ijli (meninggal 261) dan Tadhkirah al-Huffaz oleh al-Dhahabi, atau autoriti yang dicela sahaja, contohnya Kitab al-Du'afa' wa al-Matrukin oleh al-Nasa'i dan Kitab al-Majruhin oleh Muhammad b. Hibban al-Busti (meninggal 354). Dua lagi karya dalam bidang ini yang merangkumi sejumlah besar perawi, baik yang disahkan mahupun yang dicela, ialah Mizan al-I'tidal karya al-Dhahabi dan Lisan al-Mizan karya Ibn Hajar.

The work of al-Dhahabi was not left unedited; al- Khazraji (Safi al-Din Ahmad b. 'Abdullah, d. after 923) summarised it and also made valuable additions, producing his Khulasah. A number of similar works deal with either trustworthy reporters only, e.g. Kitab al-Thiqat by al-'Ijli (d. 261) and Tadhkirah al-Huffaz by al-Dhahabi, or with disparaged authorities only, e.g. Kitab al-Du'afa' wa al-Matrukin by al- Nasa'i and Kitab al-Majruhin by Muhammad b. Hibban al-Busti (d. 354). Two more works in this field which include a large number of reporters, both authenticated and disparaged, are Mizan al-I'tidal of al- Dhahabi and Lisan al-Mizan of Ibn Hajar.