This koan was randomly selected (https://www.cincinato.org/koans/randomkoan_en.php). It is unfamiliar to me, although it is commonly referenced online based on a brief search - so many references that I'm unable to determine the origin. I would be interested if anyone knows where the original translation was published.
It's very beautiful and poetic. Moreso than many koans. Although it still has me deep in thought 30 minutes after reading it. It seems that understanding and making peace with our relationship to not-being (some future state of nothingness) is required to fully appreciate what it means to be in the instant we are now.