I'm not a huge Hemingway fan, but he's completely right on this one. The wit in me would add, "or you may end up in jail, charged with murder." Mwahaha!
"Do not be quick with your mouth, nor let your heart speak rashly before the true God, for the true God is in the heavens but you are on the earth. That is why your words should be few." Ecclesiastes 5:2