Strike a wall with a sledge hammer and nothing happens, or does it? If you hit a concrete wall with a sledge hammer nothing apparently happens, at first. And even if you keep on hitting it there doesn’t seem to be any effect… but what you can’t see, is that the blows of the sledge hammer and causing invisible fractures; micro fractures inside the wall, which is weakening its structure. And eventually these fractures become so widespread that if you keep on striking the wall suddenly collapses.

Paul Valler, sermon illustration at FBC 20/3/22