Abu Bakr al-Khallal was one of the Students of Ahmad bin Hanbal's (Rahimahullaah) students, His documentation on al-Imaam Ahmad bin Hanbal's views eventually reached twenty volumes and ultimately lead to the preservation of the Hanbali school of Islamic law. He was considered the principal Hanbali scholar of his time. Ahmad bin Muhammad bin Harun bin Yazid al-Baghdadi, better known as Abu Bakr al-Khallal, was one of the Greatest Jurist of his time.
 
al-Khallal's exact date of birth is not known. He died in 923 at the age of 78, which means that he must have been born during Ahmad Ibn Hanbal's (Rahimahullaah) twilight years. The Oxford International Encyclopedia of Legal History estimates Ahmad bin Muhammad bin Harun bin Yazid al-Baghdadi's year of birth as 848.

Aside from his legal efforts, virtually nothing is known of al-Khallal's life. During his efforts to compile the views of Ahmad bin Hanbal, al-Khallal ended up spending periods of time living in Fars Province, Syria, and Mesopotamia. According to the historian al-Imaam al-Dhahabi, there was no such thing as an independent Hanbali school of law prior to al-Khallal's efforts at compiling Ahmad bin Hanbal's views. al-Khallal's status within the school was not universally accepted, and he and his students were often in conflict with fellow Hanbali, al-Hasan ibn 'Ali al-Barbahari and his students.

al-Imaam adh-Dhahabi stated that "Before him (al-Khallal) there was no independent school of the Imam's; not until he followed up Ahmed bin Hanbal's texts, wrote them down and checked their proofs after 300 A.H.
The 20th-century Hanbali jurisprudent Badran called al-Khallal's collection "the very root of the Hanbali school, from which sprang all later books of Hanbali jurisprudence."
as-Sunnah is one of the Many writings on Abu Bakr al-Khallal printed by al-Farooq al-Hadith (Cairo) in two volumes on yellow paper.