Why Make Offerings to the Sangha?

Bodhisattva Kasyapa said to the Buddha: "Oh World Honored One! If is the case that Nirvana, the Buddha-Nature, the Illimitable, and the Tathagata are one and the same, why do we say 'Three Refuges'?"

The Buddha said to Kasyapa: "All beings fear the birth and death. So, they seek the Three Refuges. By Three Refuges, we mean Buddha-Nature, the Illimitable, and Nirvana. Oh, good man! There are cases in which the name, Dharma, is one, but the meaning differs. There are cases in which the names of the Dharma and the meanings are both different. We say that the name is one, but the meanings differ. This refers to the situation where we say that the Buddha is eternal, Dharma is eternal, and the Bhiksu is eternal. Also, Nirvana and space are eternal. This is the case where the name [word (eternal)] is one, but the signification is different. We say that both the word and signification differ. The Buddha is called 'Enlightenment', the Dharma is called 'No-Awakened', the Sangha is 'Harmony', and Nirvana 'Emancipation'. Space is called 'unsafe' and also 'not-covered'. There are cases in which the word and the signification both differ. Oh, good man! The case of the Three Refuges is also like this. The word and the signification both differ. How can we say one? That is why I said to Mahaprajapati [the Buddha's aunt, who raised him]: ‘Oh, Gautami! Do not make offerings to me; make them to the Sangha! If the offerings are made to the Sangha, this amounts to make offerings to the Three Refuges’. Mahaprajapati answered, saying: ‘Among the priests, there are no Buddha and no Dharma. How can we say that the offerings made to the Sangha constitute offerings made to the Three Refuges'? I said: 'If you do as I say, this will mean that you have made offerings to the Buddha. For purposes of emancipation, offering is made to Dharma. When all the priests receive it, this is an offering made to the Sangha’. Oh, good man! At times the Tathagata speaks about one thing and makes it refer to three; he talks about three and makes it refer to one. All such things are what have to do with the world of all Buddhas. They are not what Sravakas and Pratyekabuddhas can understand."

Read more in Nirvana Sutra – Chapter 7 – On The Four Aspects.