Our words are binding.

When we say something, if we don't say Bli Neder, it takes on a very serious status.  If a person says, "I am never going to eat ice cream again" it takes on the status of a neder, and ice cream becomes traif to that person.  We have to be careful not to say something that we do not mean because it will effect us in a very negative way. from the Shiur on Naaleh: Parshat Matot & Masei: Science of Speech
Teacher: Mrs. Shira Smiles Class: Parsha for Our Lives 5770
 
When we commit our food to our sponsor, we are making all other food traif.