Kill before being killed

[Katherine Eirene Ulrich]

In a fourteenth century commentary on the Tamil Jain text NIlakEci (verse
286), a woman decides to push her husband off a cliff before he kills her.
She refers to a 'wise saying':

taR kolliyai muR kolliya, kill before the killing of oneself.

Does anyone know where this proverb comes from?  It is possible that the
commentator took liberties with an existing proverb or even invented it,
but it would be very useful to identify a source.

(btw, she does kill him, and goes on to become a Buddhist nun)

Thanks in advance for any suggestions,

Katherine Ulrich
keulrich at midway.uchicago.edu