Use a tripod and the timer

I like natural light. Flash has its place and if you want to light subjects that are close to you then flash does very nicely. It's no use taking flash if your subject is in the distance. So here are two examples of distant subjects. Alright the subjects are the same and the photos were taken within a few seconds of each other but you get the idea.

It works whether the lighting is artificial or natural. It could be that light was streaming through the window or it could be that the lights in the church are directed towards the altar. It doesn't really matter. The result is that the bride and groom are well lit. The problem without flash is that there is not enough light to allow you to hold the camera. Camera shake occurs because the shutter is open for so long. The answer is to use a tripod and to use the timer so that there is no shake from pressing the camera shutter.

Happy snapping