You cannot bump a glass of water and spill poison:
Rom 3:13 “Their throats are open graves; their tongues practice deceit.” “The poison of vipers is on their lips.”
James 3:8 but no man can tame the tongue. It is a restless evil, full of deadly poison.
Matt 12:33-34 “Make a tree good and its fruit will be good, or make a tree bad and its fruit will be bad, for a tree is recognized by its fruit. You brood of vipers, how can you who are evil say anything good? For out of the overflow of the heart the mouth speaks.”
Jesus is telling us that if poison comes out our mouth, it was in the heart first.