[seanhunter]

That's absurd.

If God exists then God holds you accountable for your actions whether you swear or not, whether you use a Bible, Carl Sagan, Dr Seuss or a copy of TCP/IP Illustrated by W Richard Stevens.

If God doesn't exist then it clearly doesn't matter what document you swear on at all, because the document is just a signal of values in that case.

Either way you are legally bound by the oath you have made and if you broke it the authorities would be able to enforce that against you to the extent enabled by law regardless of what document you use or indeed no document at all.

The document is (like the ceremony itself) just an artifact that is part of the ritual which is a public observance of a binding promise. In that context, choosing one that has personal meaning makes total sense, whether it is a religious text or something else.