 Upon the development of international trade , the elementary principles of credit and banking were developed . Both Jewish and Italian merchants had regular banking agents in Syria , who transacted business on behalf of their masters . Bills of exchange were also used by them in their dealings with one another and money was deposited in various banking centers throughout Syria . The encouragement of trade and industry provided the Ayyubid sultans with the funds needed for military expenditure as well as for developmental and everyday lifestyle works . Special attention was made to the economic state of the empire under al @-@ Adil and al @-@ Kamil . The latter maintained a strict control over expenditure ; it is said that on his death he left a treasury which was equivalent to the budget of one full year . 
