The longstanding custom in India that spawned Buddhism is called dana (generosity, giving, charity). It is on account of alms giving that a revolutionary spiritual movement was able to arise in ancient northern India. This movement of wandering ascetics (shramanas) countered the established temple priests who promoted a staid, superstitious religion of rites and rituals founded on the unquestioned authority of the Vedas.
If all this sounds strikingly familiar to the story of Jesus and the Old Testament Philistines, substituting the Buddha and the Vedic brahmins, it is. Much of the lore of Christianity is lifted from the best other religions had to offer, be they Mithras, Pagans, Egyptians, or mystics of India and the Far East. For Jesus and the apostles as well, dana was the foundation for their movement.
In India the custom of giving support to spiritual seekers, whatever their inclination, is key to the arising of the most spiritual society in the world. But what is the significance of giving a handful of rice? When it is given not to the individual but to the Sangha (as represented by the saffron robe being worn by an ordained member of the Sangha or Order), the benefits are hard to fathom. The Buddha called the Arya Sangha (the Order of Noble or Accomplished disciples) the "unsurpassed field of merit for the world."
That Noble Order is not limited to ordained members but rather includes all accomplished members -- saints who have achieved any of the four stages of enlightenment. For with enlightenment comes purification of character by degrees. The lowest of the enlightened individuals is the stream-enterer who has seen nirvana and experienced a radical transformation of view: that person is sure to win freedom from rebirth in no more than seven lives. That is because the foundations for repeated becoming have been weakened. The grip of the mental defilements has been partially destroyed.
To give with the intention of giving to the Sangha, as represented by someone on alms round, is to give to all such individuals collectively.
When that karma ripens, one is reborn again and again in fine material worlds, celestial (akasha-devas) and mundane (bhumi-devas). One forms the basis for material wealth. That is to say, not only is one born wealthy but has the merit to remain wealthy. Others may come by hard won money only to lose it in the absence of merit that sustains wealth.
In fact, all of the wished for and welcome things ordinary, uninstructed worldings long for are possible to gain by giving -- long life, beauty, pleasure, status, rebirth in the heavens. These five are desirable, agreeable, pleasant, yet hard to obtain in the world. But they can be obtained by skillful karma, a fundamental form of which is giving.