Abul Qasim Husain ibn Ruh (305 A.H. - 326 A.H.).  Abu Ja'far's daughter, Umme Kulsum, has related as follows "Husain ibn Ruh was my father's agent for many years.  He looked after the property and conveyed his secret messages to those concerned.  He was most zealous in the service of my father, who trusted him implicitly." 

Although her father had another friend and loyal patron, Abu Ja'far ibn Ahmad, he saw fit to choose Abul Qasim Husain ibn Ruh to be his successor, and his appointment was very welcome.  He was esteemed by everyone and was acknowledged as a most learned man.  He died in the year 326 A.H., and his grave is near the house of Ali ibn Ahmad Nubakhti, at a point beyond the Shawk bridge and towards the city gate at Baghdad.