He asked the old man for some advice.
The old man turned to him: ‘Have you ever washed utensils?’
What an odd thing to ask! Mildly irritated he said, ‘Yes, what of it?’
‘What did you learn?’
‘What is there to learn from it? All that one does is to scrub it clean.’
The old man smiled at him: ‘Yes, you’re right…but it’s done harder on the inside than on the outside.’
Source: Strictly not a word-by-word translation of the original from Pinterest, possibly a zen story.