Argument from biblical miracles
The argument from biblical miracles states (more or less) that because the Bible claims that people witnessed miracles performed right in front of them by Jesus, we can therefore believe that they happened—which confirms Jesus's claims to be God. David Hume criticised belief in miracles based on testimony in his essay Of Miracles because it is far more likely that the supporting testimony is incorrect.
(Double) Standard of Evidence
Since there can be no physical evidence of a man walking on water, or feeding 5000 with five loaves and two fishes, or turning water into wine, we are left solely with testimonial attestation of these events.
Imagine taking a number of tribesmen from New Guinea and subjecting them to a magic show. Afterward, it would be possible to collect as many testimonies as desired to the "fact" that, for example, the magician was beheaded by a guillotine, but was re-integrated and completely unharmed several minutes later. These testimonies are contemporary (indeed, as contemporary as is possible) and mutually corroborative, Moreover, these witnesses could be questioned to any degree. What would be our reaction? Would we take these testimonies as evidence and conclude, based only on them, that the magician really did have his head cut off and survive? Or would our incredulity at the likelihood of the event override the testimonies and lead us consider other alternatives (the tribesmen were fooled, they aren't remembering correctly, they're lying, etc.).
Would adding centuries of possible embellishment and distortion make the testimonies more, or less, credible?
The only reason such submissions are accepted when it comes to miracles is that the believers' incredulity are overridden by their a priori assumption that their god, or Jesus, is all-powerful; the testimonies are worthless without it. This will shift the discussion in that direction.