Why is Musnad Ahmad not like other Sahih Books?

Question

So as the title says, why Musnad Ahmed not in form like other Sahih Hadith books in which hadiths are listed based topic wise suchs as book of purification, book of prayer and so on? Does anybody know the reason, if there is one?

Thanks, Hassan

Answer 1

The answer is simple as the title says it is a musnad المسند which is classified by the sanad the first narrator (the narrator -Sahabi()- on whom's authority a hadith was transmitted).

A distinction between books of the Sunnah according to their classification and order of contents

In the fatwa #61637 on a distinction between as-Sihah الصحاح (plural of Sahih), as-Sunan السنن (plural of Sunah, but the books are all called Sunan) al-Masaneed المسانيد (plural of Musnad). al-Mosannafat المصنفات (plural of Mosannaf) and al-Ma'aajim المعاجم (plural of Mu'jam) on islamweb you may find the following general or simplified distinction:

• Sahih books:

فإن الصحاح تمتاز بعناية مؤلفيها بجمع صحيح الحديث وترك ضعيفه وترتيب الحديث حسب الموضوعات، كما عمل البخاري ومسلم.
Al-Sihah is distinguished by the carefulness of its authors in collecting authentic hadiths, leaving weak ones, and arranging hadiths according to topics, as Al-Bukhari and Muslim did.

Note that even if Muslim arranged his book the headers and chapter titles we find in today's editions are those of imam an-Nawawi from his commentary. In fact each commentator of his book used his own headers and titles, this leads to the conclusion that at least Muslim didn't set the chapter titles in his book. Further both al-Bukhari and Muslim ordered the ahadith inside each "chapter" based on the level of authenticity and trust, so the first hadith is always the one having the most reliable narrator chain.
One major difference between both is that Muslim often shows more details in the chain so he may compile a hadith with the same wording from different chains, just by pointing at the different paths of it.
Scholars say that the ahadith which imam al-Bukhari mentioned -without sanad/narrator chain- at the beginning of each chapter (they are also called al-Mo'allaqaat the attachments or maybe the commentaries) are mostly authentic or at least of a high level of authenticity. Sadly sunnah.com ignores them and doesn't offer a translation.

• Sunan books

وأما كتب السنن فإنها اعتنت بجمع الأحاديث حسب الموضوعات، ولم يلتزم مؤلفوها بالاقتصار على الأحاديث الثابتة، بل أدخلوا فيها بعض الأحاديث الضعيفة، كما عمل الترمذي وأبو داود.
As for the books of Sunan, they took care of collecting hadiths according to topics, and their authors did not commit to limiting themselves to established hadiths, but rather included in them some weak hadiths, as at-Tirmidhi and abu Dawud did.

Basically one could say a Sunan book is a hadith collection which is divided into chapters according their topics, in which there's no restriction on a high level of authenticity of the content.
Most authors of the Sunan say something like we have gathered all ahadith that scholars have used as evidences (especially when it comes to fiqh rulings, some of these evidences are rather da'if ahadith). An example of such a claim will be provided later.
Imam at-Tirmdihi's Jami' (nevertheless it is always referred to being one of the Sunan) offers a certain qualification of most ahadith which follows his own terminology.

• Musnad books:

وأما المسانيد فإنها تمتاز بأن أصحابها جمعوا مسند كل صحابي على حدة من دون اعتبار لحال الحديث صحة وضعفاً ومن غير ترتيب موضوعي، كما عمل الإمام أحمد والحميدي.
As for the musnads, they are distinguished by the fact that their authors compiled the musnad of each companion separately without regard to the condition of the hadith, whether it is correct or weak, and without an objective arrangement, as imam Ahmad and al-Hamidi did.

A Musnad is a hadith collection which is ordered according the Sahabi on whom's authority ahadith were narrated.
Imam Ahmad has chosen to start his book by the 10 sahabah () who were promised paradise:

It is organized into compilations of the hadiths narrated by each Companion (Sahabi), starting with the 'asharah mubashsharah ("the ten who were promised Paradise"). This highlights their status and the efforts they made to preserve the ahadeeth of the Messenger of Allah. It is said by some that Ahmad ibn Hanbal made a comment in regard to his book which reads as follows: "I have only included a hadith in this book if it had been used as evidence by some of the scholars." (wikipedia)

• Mu'jam books:

وأما المعاجم فإنها تمتاز بجمع المؤلفين أحاديث رووها حسب ترتيب الصحابة أو شيوخهم، حيث يأتي المؤلف بمرويات كل شيخ أو صحابي وحده من دون عناية بالموضوعات ولا اعتبار للصحة مثل ما عمل الطبراني في الأوسط، فقد جمعه حسب شيوخه، وفي الكبير فقد ذكر ما تيسر له عن كل صحابي.
As for Ma'ajim, they are distinguished by the authors’ collection of hadiths that they narrated according to the order of the Companions or their sheikhs, where the author brings the narrations of each Sheikh or Sahabi () (Companion) alone without concern for topics and no consideration of authenticity like what al-Tabarani did in the middle, he collected it according to his sheikhs, and in al-Kabir he mentioned what was easy for him about All my companions.

I don't know of any other author of a Mu'jam except with imam at-Tabarani, whom authored three of them.

• Mosannaf books:

وأما المصنفات فإنها تمتاز بجمع الأحاديث حسب الموضوعات مع إضافة الآثار المروية عن السلف في ذلك الموضوع دون التزام بالصحة، فاجتمع فيها المرفوع الصحيح وغيره مع الموقوف والمقطوع، كما عمل عبد الرزاق وابن أبي شيبة في مصنفيهما.
As for al-Mosannafat, they are distinguished by the collection of hadiths according to topics with the addition of the narrations narrated from the predecessors on that subject without commitment to authenticity, so they combined the authentic and others with the suspended and the cut off, as abd al-Razzaq and ibn abi Shaybah did in their compilations.

Basically al-Mosannaf is a collection of narrations that include both hadith and athar (narration of what sahaba or tabai'yn said or did) which is ordered according topics.