In the context of a discussion of the obligation of burying a corpse found on the way:
And an exception is made for the met mitzvah. Should the kohen encounter an abandoned corpse, and no one else is available to bury it, he is commanded to ignore the prohibition against contact with the dead, and he must bury that corpse himself.
One commentary (don't have it handy sorry) linked it to performing mitzvot that are neglected (i.e., 'dead' to most Jews/people). There are Mitsvot that has no one to "support them" like a corpse that has no one to bury it.
I enjoyed this idea and wondered how to put it in practice. Could someone tell me how to do so?