Bodhidharma's Vast Emptiness (BCR1)(BS2)

KOAN:

Emperor Wu asked the great teacher Bodhidharma, “What is the first principle of the holy teaching?”
Bodhidharma said, “Vast emptiness, nothing holy.”
“Who are you, standing here in front of me?” asked the emperor.
“I don’t know,” said Bodhidharma.
The emperor didn’t understand.

—Blue Cliff Record, Case 1, & Book of Serenity, Case 2