the ascetic.
He ranked among the foremost jurists and devoted worshippers.
He travelled in search of knowledge and received hadith from Sufyan ibn ʿUyaynah, Ibn Abi Fudayk, ʿAbd al-Wahhab ibn ʿAtaʾ, Hafs ibn ʿAbd al-Rahman, Abu Usamah, Abu Dawud al-Tayalisi, Abu ʿAmir al-ʿAqadi, Muhammad ibn ʿUbayd al-Tanafisi, ʿAbd Allah ibn al-Walid al-ʿAdani, ʿAmir ibn Khidash, and their peers.
He gathered narrations and authored works.
Those who narrated from him include: Ahmad ibn al-Azhar, Sahl ibn ʿAmmar, al-ʿAbbas ibn Hamzah, Muhammad ibn Shadhil, Ibrahim ibn Muhammad ibn Sufyan the jurist, Ahmad ibn Nasr al-Khaffaf, Ismaʿil ibn Qutaybah, Zakariyya ibn Dallawayh, and many others besides.
Zakariyya ibn Dallawayh said: When Ahmad ibn Harb sat before the barber to have his moustache closely trimmed, he would engage in tasbih (repeating “Subhan Allah”), until the barber would say to him, “Be silent for a moment.”
He would reply, “Just do your work.”
Sometimes the barber even cut his lip without his realizing it.
Al-Hakim said: Abu al-ʿAbbas Ahmad ibn ʿAbd Allah al-Sufi narrated to us; Abu ʿAmr Muhammad ibn Yahya related to me, saying:
“Ahmad ibn Harb passed by some boys who were playing. One of them exclaimed, ‘Be still! This is Ahmad ibn Harb, the man who never sleeps at night.’
He seized his beard and said to himself, ‘Children stand in awe of you, and yet you sleep?’
From that night on he spent the entire night in worship until he died.”
Zakariyya ibn Harb also said: “My brother began fasting while he was still in the Qur’an school; when he reached puberty he performed the pilgrimage with his brother al-Husayn ibn Harb. They then stayed in Kufa to seek knowledge, and likewise in Basra and Baghdad.
After that he devoted himself to worship without tiring. He turned to preaching and admonition, urged the people to worship, and they flocked to his gatherings.
He composed the Book of Forty Hadiths (Kitab al-Arbaʿin), the Book of Allah’s Dependants (Kitab ʿIyal Allah), and the Book of Asceticism (Kitab al-Zuhd),