Is that Really Yours?

A Zen student asked his teacher.  “What is the most valuable thing of this world?”
The teacher replied.  “Give me your finger and I will show you.”
With this the student left the teacher.
Upon return the student stood before the teacher bowed and said “this is my finger, I have severed it from my own hand and I now give it to you, to show how important this question is to me.”
The teacher without looking at it took the finger and threw it over his shoulder.  “This is not your finger if it were your finger it would still be attached to your hand.”
Crying the student replied “What could we have learned here, I have mistakenly cut from my own hand the finger which no longer belongs to me.”
“We have learned” said the teacher “That your finger is not the most valuable thing of this world.”