Prophecy -Validate by foretelling future?

Rambam(Letter to Yemen):[translated by Abraham Halkin][The following incident we have verified and know to be true, because it occurred in recent times. About fifty years ago or less, a pious and virtuous man by the name of Moses al-Darri came from Darral to the province of Andalusia to study under Rabbi Joseph ha-Levi ibn Migash, of blessed memory, of whom you have very likely heard. Later he left for Fez, the center of the Maghreb. People flocked to him because of his piety, virtue, and learning. He informed them that the Messiah was about to come, as was divinely revealed to him in a dream. Yet he did not pretend on the basis of a divine communication, as did the former lunatic, that he was the Messiah. He merely affirmed that the Messiah would appear. Many people became his adherents and put their faith in him. My father and master, of blessed memory, endeavored to dissuade and discourage people from following him. However, only a few were influenced by my father, while most, nay, nearly all clung to R. Moses. Finally he predicted even events that would come true no matter what was going to occur. He would say: “I was informed yesterday that this and this would happen,” and it did happen exactly as he predicted. Once he foretold a vehement rain for the coming Friday and that the falling drops would be blood. This was considered a sign of the approaching advent of the Messiah, of which the text says: “[ will set portents in the sky and on earth, blood and fire and pillars of smoke” [Joel 3:3]. This episode took place in the month of Marcshevan. A very heavy rain fell that Friday and the fluids that descended were red and viscous as if mixed with clay. This miracle convinced all the people that he was undoubtedly a prophet. In itself it is not inconsistent with the tenets of the Torah, for prophecy, as I have explained, will return to Israel before the messianic advent. When the majority of the people put their trust in him, he predicted that the Messiah would come that very year on Passover eve. He advised the people to sell their property and contract debts to the Muslims with the promise to pay back ten dinars for one, in order to observe the precepts of the Torah in connection with the Passover festival, for they would never see them again, and so they did. When Passover came and nothing transpired, the people were ruined, as most of them had disposed of their property for a trifling sum, and were overwhelmed with debt. When the gentiles in the vicinity and their serfs learned of this hoax they were minded to do away with him, were they to locate him. As this Muslim country no longer offered him protection, he left for Palestine where he died, may his memory be blessed. When he left he made predictions, as I was told by those who saw him, concerning events both great and small in the Maghreb, which were later fulfilled.