As has been mentioned above, the Buddha said that there were four necessities of life: clothing, food, shelter and medicine.
The Buddha suggested that the basic source of food for bhikkhus was that received on the morning alms round (pi.n.dapaata).
This daily dependence on alms food reminds both the bhikkhus and the lay devotees of their interdependence and prevents the bhikkhu from becoming too isolated from the lay community.
He meets them every day and eats the food that they share with him.
Several important rules are concerned with this as well as a major section of the Sekhiya Training rules.
(See below; see also story about Ven. Assaji.)
An alms round is not considered begging, for the bhikkhu does not solicit anything but is ready mindfully to receive any alms that lay people may wish to give. Although alms food may sometimes be meager, the bhikkhu is always expected to be grateful for whatever he is given.
It is surprising how particular we can be about what food we like to eat; and what complications that can cause.
This is reflected in the way rules concerning edibles are arranged, which may seem very complex especially when the bhikkhus life is supposed to be so simple.
It should be borne in mind that the rules often deal with extraordinary circumstances and try to prevent them from becoming the norm.
He gave this reflection: Properly considering almsfood, I use it: not playfully, nor for intoxication, nor for putting on weight, nor for beautification;
but simply for the survival and continuance of this body, for ending its afflictions, for the support of the chaste life, (thinking) I will destroy old feelings (of hunger) and not create new feelings (from overeating).
Thus I will maintain myself, be blameless, and live in comfort." [OP p.46; (Paali: M. I, 10; A. III, 387)]
The bhikkhu may also voluntarily undertake the special dhuta"nga (tudong in Thai) practices.
These are more usually seen among forest monks and are distinctive of their way of practice.
For example, they always try to go on alms round; they eat the collected food out of their alms bowl in one sitting; and may refuse late come food. (See also dhutanga in the Glossary.)