Ahmad bin Abdullah, Muhammad al-Habib, or Abul Hussain, surnamed at-Taqi (God-fearing), also called Taqi Muhammad, was born in 174/790 and ascended in 212/828. He lived secretly with his followers as a merchant at Salamia. He is also called Sahib al-Rasail (Lord of the epistles). He however retained the services of Abdullah bin Maymun (d. 260/874) as his hujjat.
W.Ivanow writes in "Ismailis and Qarmatians" (JBBRAS, Bombay, 1940, p. 73) that, "The second hidden Imam, the author of the Encyclopaedia of the Ikhwanu's Safa, or Sahib al-Rasail, as he is usually referred to in the Ismaili theological works, is also known definitely as Ahmad."
Taqi Muhammad was known as an eminent Hashimite trader, making the people to flock at his residence. It suspected the Syrian governor, who communicated its report to caliph Mamun Rashid, who issued order to arrest Taqi Muhammad, but the latter had quitted Salamia in advance for few years.