"Venerable Sir, Rahula attained the end of āsavas (mental defilements) just by contemplating the earth element alone. As the Buddha said:
'Rahula, when one knows and sees the earth element as impermanent, the destruction of the āsavas occurs. I say there is nothing further to be done.'
Dear son Rahula, study the earth element until you master it. Study to know the earth element as it truly is. What people think they find is hardness and softness... From head to toe, when you feel it, do you find a person or do you find hardness? Do you find a person or softness?
Do you find limbs or do you find hardness and softness? You only find hardness and softness, right?
Hardness is earth element, softness is earth element. Is it a self that knows hardness and softness, or is it body-consciousness (kāyaviññāṇa)? Isn't body-consciousness a mental phenomenon (nāma)? Aren't hardness and softness physical phenomena (rūpa)? So there are just these two: mind and matter.
Is there a person, or just mind and matter? A deva, or just mind and matter? A brahma, or just mind and matter? Why don't we find a person? Why don't we find a deva? Why don't we find a brahma?
Yet despite not finding them, don't we still label these hardness and softness as 'person', 'deva', 'brahma'? Can we reject these labels? What exactly are we rejecting? Isn't this worth investigating?
Don't we think 'person' exists? But what we actually find is just mind and matter. Why don't we find persons, devas, or brahmas?
This requires faith to understand. If something doesn't exist, how can we cling to it?
Though we know it doesn't exist, don't we still say 'person'? Don't we still say 'son', 'daughter', 'father', 'mother'? Can we reject these conventions? We're rejecting the concept and notion... We think 'person' exists, but what we find is just mind and matter. Why don't we find a person?
If it doesn't exist, how can we cling to it? Mind and matter are also impermanent (anicca), suffering (dukkha), and non-self (anatta) - can they be objects of clinging?
That's why the Buddha said:
'Rahula, when one knows and sees the earth element as impermanent, the destruction of the āsavas occurs. I say there is nothing further to be done.'
Dear son Rahula, study the earth element until you master it. When you thoroughly understand the impermanence of the earth element, didn't the Buddha say no further practice is needed?
The earth element is physical matter, right? Water element is physical matter, right? Air element is physical matter, right? Fire element is physical matter, right?
Isn't this worth investigating? This needs to be studied, understand?
Physical matter changes and dissolves, doesn't it? Mental phenomena arise and cease, don't they?
Do we find mind and matter, or do we find their absence?
When we know their impermanence, didn't the Buddha say no further practice is needed?
How sufficient is this understanding, do you hear?
We need to strive to reach this stage. We can only abandon what we understand. How can we abandon what we don't understand? Consider this - the Rahulovada Sutta stands as testimony. This needs to be properly understood."