Answer:
The close relationship between Buddhism and trade is largely due to the reliance of the Buddhist monastic community on donations from lay supporters. Ideally, Buddhist monks and nuns were required to reject all worldly possessions and thus to depend on the lay community to supply all of their necessities, including food, clothing, shelter, and medicine. In practice, donations to Buddhist monasteries extended to a wide range of materials that were necessary to maintain resident communities of monks and nuns. Significant economic surpluses were needed to sustain large-scale Buddhist institutions, where, in return for donations, monks and nuns were available to give religious instruction.
In return for their material donations to Buddhist monasteries, donors received religious merit (punya), which was often shared with relatives, teachers, political supporters, and "all beings" (sarvasattva). Donations establishing the presence of the Buddha at particular places in the form of stupas, relics, images, and texts generated special merit, since such sacred gifts provided opportunities for more devotees to worship the Buddha's body or teachings. Wealthy merchants and powerful rulers were particularly encouraged to be very generous in return for practical benefits, such as refuge and protection from real and perceived dangers while traveling, and status or legitimacy by acting as patrons of religious institutions. Epigraphic records of donations to Buddhist stupas and monasteries in India attest to the importance of commercial and political patronage of Buddhist institutions.