Keys to Two Kingdoms

I have just returned from delivering a hundred or so leaflets inviting people to our carol services. It’s quite late in the week, but it would have been a crime to have left them undelivered. Although it was dark and wet, I noticed in one door that the house keys had been left in the outside lock. Thankfully, it was a local pastor who found them rather than a local burglar. I duly removed them and posted them back through. Doubtless, they landed on the very leaflet I had intended to deliver. As I began walking to the next house, I wondered what points I could make from this. In fact, I came up with dozens. Leafleting, though good for the body, offers little challenge to the mind. I settled for this one:

Two keys were pushed through that letter box- one unlocking a temporal kingdom, the other an eternal kingdom. The latter will probably be discarded within seconds, the former cherished with relief.

What does it profit a man if he gains the whole world but loses his own soul?