Ajaan tells another story of the man and the buffalo:
It's just like a farmer who wakes early in the morning while it is still dark outside, in order to plow his field. He goes to the pasture and takes a buffalo back, hitching it to the plow and starting to plow the field. As he goes about plowing the field, the sun comes up and he sees that this is not his buffalo! Realizing this, he quickly lets the buffalo go free.
The meditator taking the body and mind as being permanent, satisfying and belonging to self is like the farmer taking the buffalo to be his own. The realization of impermanence, suffering and non-self is like the sun coming up and the farmer seeing that this is not his buffalo. The letting go by the meditator is like the man setting the buffalo free.