There is a subtle message behind the exchange between Chao-chao and the Monk. To understand that this is not simply a superficial conversation of meals is vital. The metaphor here is that of feeding someone with knowledge. When the master asks if has eaten his rice gruel, in fact, he’s asking if he has felt he has learned anything during his travels. When the monk replies he feels he has, the master asks him to forget everything he has learned, to wash it all away.

Washing the metaphorical bowl of the mind may seem very easy, but in actuality can be quite difficult. Sometimes, it is very hard to get rid of all the things we have previously learned. However, this is a central focus in Zen. Becoming boundless and nothingness requires the ability to strip down everything we are. Although those gems of knowledge we have learned over the years can be elegant, beautiful, and inspiring; the goal of Zen Buddhism is to empty oneself. Thus, the importance of forgetting all prior accomplishments and understandings is very important. Rather than collecting precious moments, being in the present at all times, in the moment, will lead to true enlightenment.

Safe Journeys,
-Clyde

Koan and commentary surmised from:

http://www.ordinarymind.com/koans_frameset.html