Shundo David Haye – Zen Priest

Yangshan asked the magistrate Lu, “I’ve heard that the magistrate had an understanding while looking at a sūtra. Is that so?”
The magistrate said, “Yes. Your disciple was looking at the Nirvāṇa-sūtra, where it says, ‘Enter nirvāṇa without eradicating the afflictions.’”
The master raised his whisk and said, “If it’s this, how will you enter?” The magistrate said, “The word ‘enter’ isn’t necessary.”
The master said, “The word ‘enter’ is not for the magistrate.” Wherepon the magistrate rose and left.

How can you enter somewhere you already reside?