In Hamburg, Jarrah had a succession of living accommodations, but he apparently never resided with his future co-conspirators. It is not clear how and when he became part of Atta's circle. He became particularly friendly with Binalshibh after meeting him at the Quds mosque in Hamburg, which Jarrah began attending regularly in late 1997. The worshippers at this mosque featured an outspoken, flamboyant Islamist named Mohammed Haydar Zammar. A well-known figure in the Muslim community (and to German and U.S. intelligence agencies by the late 1990s), Zammar had fought in Afghanistan and relished any opportunity to extol the virtues of violent jihad. Indeed, a witness has reported hearing Zammar press Binalshibh to fulfill his duty to wage jihad. Moreover, after 9/11, Zammar reportedly took credit for influencing not just Binalshibh but the rest of the Hamburg group. In 1998, Zammar encouraged them to participate in jihad and even convinced them to go to Afghanistan. Owing to Zammar's persuasion or some other source of inspiration, Atta, Binalshibh, Shehhi, and Jarrah eventually prepared themselves to translate their extremist beliefs into action. By late 1999, they were ready to abandon their student lives in Germany in favor of violent jihad. This final stage in their evolution toward embracing Islamist extremism did not entirely escape the notice of the people around them. The foursome became core members of a group of radical Muslims, often hosting sessions at their Marienstrasse apartment that involved extremely anti-American discussions. Meeting three to four times a week, the group became something of a "sect" whose members, according to one participant in the meetings, tended to deal only with each other. Atta's rent checks for the apartment provide evidence of the importance that the apartment assumed as a center for the group, as he would write on them the notation "Dar el Ansar," or "house of the followers." In addition to Atta, Binalshibh, Shehhi, and Jarrah, the group included other extremists, some of whom also would attend al Qaeda training camps and, in some instances, would help the 9/11 hijackers as they executed the plot: Said Bahaji, son of a Moroccan immigrant, was the only German citizen in the group. Educated in Morocco, Bahaji returned to Germany to study electrical engineering at the Technical University of Hamburg-Harburg. He spent five months in the German army before obtaining a medical discharge, and lived with Atta and Binalshibh at 54 Marienstrasse for eight months between November 1998 and July 1999. Described as an insecure follower with no personality and with limited knowledge of Islam, Bahaji nonetheless professed his readiness to engage in violence. 
The four became somewhat of a sect meeting 3 to 4 times a week and what was it that Atta would write on the rent checks?
Dar el Ansar, which means house of the followers