draw a line in the sand vs prove

draw a line in the sand

verb
  • To lay down a challenge; to provide a test of commitment (often one which carries a high risk) to a cause. 

  • To create a real or artificial boundary or distinction between (two places, people or things). 

  • To indicate the threshold or level above which something will become unacceptable or will provoke a response; to create a boundary and imply or declare that its crossing will provoke a (negative) response. 

prove

verb
  • To put to the test, to make trial of. 

  • To demonstrate that something is true or viable; to give proof for. 

  • To ascertain or establish the genuineness or validity of; to verify. 

  • To determine by experiment which effects a substance causes when ingested. 

  • simple past tense of proove 

  • To turn out; to manifest. 

  • To turn out to be. 

noun
  • The process of dough proofing. 

How often have the words draw a line in the sand and prove occurred in a corpus of books? (source: Google Ngram Viewer )