One of the greatest compilations of hadith is the Musnad by Imam Ahmad bin Hanbal, which is organised into compilations of the ahadith narrated by each Companion, starting with the the ten who were promised Paradise.
The scholars have praised the Musnad of Imam Ahmad. Al-Hafiz Abu Moosa al-Madeeni he said: “This book is an important source and trustworthy reference for the scholars of hadith, as he (Imam Ahmad) selected from a large number of hadith he came across and the plentiful reports he heard, and he put a great deal of effort into making it a prominent, leading and reliable source. When disputing an issue, it is a refuge and a source of help.