I added yeast to a recipe calling for baking soda, what will happen?
Yeast is a levening agent that needs some time to do its job. It eats sugar and makes CO2 gas to ride your bread.

Baking soda and baking powder are chemical levening agents. They'll make your bread rise while its baking.

If you out in yeast as well as BP and/or BS, and you bake it right away, probably nothin will happen and it will be a bit more nutritive, if you wait, you might find yourself with a handful of a mess when it rises way too much.