I'm trying to find the source for a little story told by Ajahn Atulo in Gifts He left Behind. Here is the story,
Ven. Sariputta had just come out of the attainment of the cessation, and the Buddha asked him, 'Sariputta, your skin is especially bright, your complexion especially clear. What is the dwelling place of your mind?'
"Sariputta answered, 'My mind's dwelling place is emptiness.'
Where in the Canon is this story?