Pesachim Daf 27

Rabbi Yehuda is of the opinion that only burning is a valid means to destroy chometz. He bases this on a logical inference (kal vechomer) from nosar ( leftover parts of a Korban) If  nosar which doesn't encompass any ongoing transgressions till its destroyed, needs to be destroyed specifically by fire, surely chometz which has ongoing transgressions (bal yeraeh and bal yematzeh) surely needs to be destroyed specifically by fire. The Chachamim argued "kol din sheatah dan tchilaso lehachmir vesofo lehakel aino din"  whenever one intends to learn a stringency and it ends up a leniency in is not valid.

This is an important message, for in order to be stringent one must always look at the repercussions lest it turn out to be a leniency in the end.