Deuteronomy 18:22 suggests that a way of recognizing false prophets is to check whether their predictions are falsified.

However, there is no mention of unfalsifiable predictions; one would have expected an omnipotent being to reveal this important criterion, but there is no mention of it.

Falsifiability was first made explicit by philosopher Karl Popper, but implicit awareness of this principle is undoubtedly much older. Lucian of Samosata seems half-aware of that principle, as is evident from his discussion of Alexander of Abonutichus.

A of A had prophesied that if Roman Emperor Marcus Aurelius threw two lions into the Danube, a great victory would result against the Marcomanni. However, it was the Marcomanni who won the great victory. A of A, when asked about that, responded that the god had indeed predicted a victory, but did not say which side would win. Which Lucian found to be a tired old excuse reminiscient of what the Oracle of Delphi had responded to King Croesus when it was his empire that fell.

However, he did not state the more general conclusion that these two prophecies had been short on falsifiability -- that they would be confirmed if either side had won.