Shopping at Midnight

The Reading:

Shoyoroku - Case 76: Shuzan's Three Verses

Shuzan instructed his assembly and said, 
  "If you attain the first verse, you will be the teacher of buddhas and
   patriarchs. If you attain the second verse, you will be the teacher of
   heaven and humankind. If you attain the third verse, you cannot save even
   yourself."
A monk asked,
  "Which verse did Your Reverence attain?"
Shuzan said, 
  "The moon is set at midnight; I walk alone through the market place of
   the city."

Discussion:

Alone in the market place at midnight... what is he shopping for?