[consp]

> If you don't have that meaning behind the oath, what is the point in using a book at all unless?

Which is why it's not done in lots of places. Here it's only a sentence which is either translated "So help me God almighty" or "That I declare and promise" (pinky swear basically)

The legal meaning is that you can be held accountable to the preceding promise. Apparently God is only there to help you since you are unable to do it yourself but has no game in the promise.