Questionable

Does anyone know what talk this story is from? There was an uneducated missionary who goes out with his companion, or maybe a mission president. They go to a house and the missionary is just scared, and inarticulate -- until he gives his testimony, at which point it is very powerful and spiritual. What is this from?

Just as an aside, a lot of hot drinks in China and other parts of Asia are called "tea" even though they aren't actually tea, and there is nothing "tea" about them.