I believe it is the Bible and a cloud of witnesses.
Hmm... But many holy books have been written all over the world, and they are all written by men. Doesn't seem very supernatural to me.
What, specifically, is it about the bible that couldn't have been replicated by man?
As for witnesses, police will tell you all about the reliability of witnesses. There are plenty of studdies out there about the realiability of people's memories, and it turns out that our memories are not that accurate: especially over time.
Are memories reliable? Expert explains how they change more than we realise
Not only that, but people are even prone to creating false memories for themselves.
How False Memories Can Affect Our Ability To Recall Events
Creating False Memories
Then there's the issue with collective false memories that are created in group settings.
Collective memory - Wikipedia
Collective representations elicit widespread individual false memories - ScienceDirect
...And the gospels were written, what, 30 years after the death of Jesus?
You know, recently my mom found an old family home video of Christmas from when I was 12. I remember that christmas very strongly! I got a lot of cool Star Wars stuff, and I even got a pet hampster with a cage that had all the tubes and stuff for the hampster to run around in!
Now, after seeing the video... Eh. I didn't get as many Star Wars toys as I remember getting, and they were small little things; nothing that epic. The hampster cage wasn't nearly as intricate as I remembered, either. It was a good christmas, but I had inflated just how good it was in my own mind, and it wasn't until after I saw a third party perspective where I saw just how different my memories had become in relation to the actual event.
That's assuming the people who wrote the unverifiable stories of the bible were telling the truth (as best as they knew it).