When your bread spoils, it is being eaten by microscopic forms of life - microbes. Toasting makes your bread less appetizing to microbes. Heat evaporates bread's moisture, making it harder for microbes to live. And a lot of the food value of the bread is turned into free carbon in the toaster, making it less a lunch for the microbes. Let it sit for 10 minutes.
Yeast is alive.
Bring 2 cups of milk to a boil, then turn it off and add half a stick of butter cut up into pieces. Let it melt. Add 2 teaspoons salt and 2 tablespoons honey. Mix it all up and let it cool. If it's hot, you'll kill your yeast.