Next, where is the Buddha-Nature that is in the Lord Buddha? In other words, where is the Buddha? We call this "place" Buddha-Kasetra. Kasetra is a Sanskrit word meaning "place" or "field." (The Pali equivalent is khetta.) "Field" refers to a place containing or holding something. In this case, where is the Buddha-Kasetra, that is, the place or area where the Buddha is? To answer, we must do so in two ways, in people language and in Dhamma language.
Buddha-Kasetra in people language: Some Mahayana texts say that there is a Buddha-Kasetra for each of the thirty thousand world systems (loka-dhatu). Every world system has a place or realm for the Lord Buddha to be, for example, in this world system there is the Pure Land (Sukhavati) where the Buddha Amitabha dwells. Each world system, of which there are thirty thousand, has its own Buddha-Kasetra and a Buddha dwells in each Buddha-Kasetra. Some schools speak of many dozens or hundreds of Buddhas in each, as if they are waiting their turn to appear in the human world.
We have been speaking in physical, worldly terms — kingdoms, realms, worlds. These are Buddha-Kasetras. When people hear of them and are pleased, they believe in them. They immediately accept that such Buddha-Kasetras exist in specific places and that specific Buddhas dwell in each one. Their faith is so strong that they want to be reborn in one of these Buddha-Kasetras. Such are the Buddha-Kasetra of people language, in material terms.
It's much easier when we speak in Dhamma language. They are all in our hearts. The Buddha-Kasetras, the fields or realms in which the Buddhas appear, are in our hearts. In Chinese Mahayana (I think but am not sure it's Mahayana), there is a saying that there are thirty thousand Buddhas in this mind. Thirty thousand Buddhas in the mind: some of you must be thinking that's crazy! Who thought up such a crazy thing? Let's see who's crazy.
Notice that the amount is the same as a few moments ago. There are thirty thousand world systems with a Buddha in each one and there are thirty thousand Buddhas in the mind. This means that the thirty thousand world systems are in this mind. Everything depends on mind, happens through the mind. Every possible world system is in the mind. The Buddha of each world system is also in the mind. It is only logical. That they say there are thirty thousand Buddhas in the mind makes perfect sense in Dhamma language.
If this is our understanding, we are immensely rich. With thirty thousand Buddhas in the mind, we don't have to clutter our necks with a mere four or five that can't help us anyway. Those external Buddhas, whether hanging around our necks or in the temples, can't help us. Only the Buddhas in the mind can help us. Namely, the knowledge or wisdom — the cleanliness, clarity, and calm — of the mind is the Lord Buddha and can truly help us. Now we have thirty thousand Buddhas and they all are genuine. They are all in our hearts. They are the most safe, the most peaceful, the most satisfying Buddha Fields. It's important that we understand where the Buddhas are, in this way, called "Buddha-Kasetra."
Others may say the Buddhas are in other world systems, in other universes, or who knows where. We say they are in our hearts. In a single mind there are thirty thousand Buddhas. Thus, our hearts are the Buddha Fields. Although true, this has become something unknown. When we are ignorant about it, it has no benefit for us.
May each of you make this very mind the dwelling place of thirty thousand Buddhas. Then, you will understand the Buddha-Kasetra in Dhamma language. Don’t bother with people language, it’s too much of a hassle. To have only a single Buddha who was born in India 2500 years ago and long ago entered Parinibbana is to be at a huge disadvantage to those who have thirty thousand Buddhas in their hearts all the time. You should be able to figure out who has the better deal.
Don’t be in a hurry to think they’re crazy. We might be ignorant, you know. Don’t forget how wise and clever the ancients were; they said certain things to make fools of us today. Please remember this: anything that we don’t understand today, that we can’t figure out with our modern way of thinking, is something they said just to make fools of us. It serves us right! So be careful. Whatever doesn’t make sense or can’t be understood in what they said or wrote should be taken as something they made up most cleverly, in order to make fools of us rather than that they be the fools. We can solve this dilemma by being careful not to be tricked by them. Don’t accept being a fool; try to be intelligent. Whatever angle is presented, whatever words or symbols are used, whatever twists or tricks they use, be mindful and understand immediately.
That’s enough on Buddha-Kasetras, the birthplaces of the Buddhas.
The best way from http://www.suanmokkh.org