The Sangha lives according to the Vinaya, a code of monastic discipline established by the Buddha. In accordance with this discipline, the monastics are alms-mendicants, living lives of celibacy and frugality.
Above all, this training is a means of living reflectively and a guide to keeping one’s needs to a minimum: a set of robes, an alms bowl, one meal a day, medicine when ill, and a sheltered place for meditation and rest.
The Vinaya creates a firm bond between the Sangha and the general public. One reason for this is that without the daily offering of alms food, and the long-term support of ordinary people, the Sangha cannot survive. Obviously, the necessary support will only be forthcoming if the Sangha provides an example that is worthy of support. This relationship creates a framework within which generosity, compassion and mutual encouragement can grow.
Dependence upon others encourages monastics to live in faith and to be content with a humble standard of living. For those who support the Sangha, this opportunity to give provides occasions for generosity and a joyful and direct participation in the spiritual life. In return the Sangha offers people spiritual guidance by verbal teachings and by its living presence.
This reflection by Ajahn Amaro is from the book, Rugged Interdependency, (pdf) pp. 4-5.