Abd al-Qadir came to Baghdad from Gilan, on the Caspian, some time in his teens, and the outline of his early life there is thin: study, poverty, and a long period of withdrawal are what the sources agree on. What is well recorded is the second half. He was a jurist of the Hanbali school, the most textually strict of the four Sunni schools of law, and he taught and preached from a madrasa placed under his direction. His sermons drew crowds large enough that he preached out of doors, and the accounts of them describe an audience that included Jews and Christians as well as Muslims.
The point worth holding on to is that his Sufism sat inside the law rather than beside it. Nile Green's history of Sufism uses him as an example of how far the developed mystical tradition was integrated with legal scholarship in this period, against the persistent modern picture of Sufism as a movement of outsiders. The works of exhortation attributed to him, chiefly a manual of the sufficiency for seekers of the path of truth and the collection called the revelations of the unseen, are addressed to disciples who are expected to keep the ritual law in full while working on the interior life.
He died in Baghdad in 1166. His reputation grew steadily after his death, and titles accumulated on it, of which the largest is al-Ghawth al-Azam, the supreme helper. The scale of that reputation across the Muslim world is out of all proportion to anything he is recorded as claiming for himself.