Rambam, Mishneh Torah, Yesodei Hatorah, Chapter 10: The miracles a prophet must perform to prove his validity

Chapter 10: The miracles a prophet must perform to prove his validity

Nature breaking miracles: A prophet which claims to have been sent by G-d, does Not need to perform a nature breaking miracle on the level of Moshe or Eliyahu or Elisha.
Rather, it suffices for him to predict the future.
The order of testing a potential prophet: Accordingly, when an individual arrives who is fit to be a prophet of G-d and he does not come to add or subtract from the mitzvah’s but rather simply to serve G-d through fulfilling the mitzvah’s written in the Torah, then he is not to be asked to perform a nature breaking miracle, such as to split the sea or revive the debt as a prerequisite to believe him. Rather, he is to be told that if he is indeed a prophet then he should predict things of the future, and if they will come true, then he will be believed. Accordingly, we do not verify and authenticate his prophecy until we see that his predictions come true.
If the prediction is not completely accurate: In order to believe the claims of the prophet his predictions must be 100% accurate. If even a small part of his predictions do not come to fruition, then he is known to be a false prophet.

The acclaimed prophet must be checked many times to make sure that his many predictions come true. If they all come true then he is to be accepted as a true prophet.

Inaccurate predictions: Although there are people who use sorcery to tell the future, there is a difference between them and a prophet: Those who use sorcery for predicting the future will never have a completely accurate prediction, and rather only part of the prediction will come to fruition. This is at best, at worst nothing will come true of their prediction. The predictions of the sorcerers is similar to straw mixed with grain and contains waste product. However, the word of G-d is pure grain without any waste product.
G-d instructed the Jewish people to only consult with the his prophets and forbade them from consulting with sorcerers and the advantage of doing so is that the prophets will give him a true prediction.
The purpose of the prophets: The function of the prophets is to inform the Jewish people of true predictions of future events, such as years of plenty and years of hunger, Years of war and years of peace. Likewise, they are there to inform the individual of his needs, such as regarding the whereabouts of a lost object. Their purpose is not to create another religion or add or detract from the mitzvah’s.

Inaccuracies in predictions of calamities: If a prophet predicts a certain tragedy or calamity to occur, such as regarding the death of an individual or a year of war and famine, and it does not happen, then this does not necessarily mean that his prophecy is inaccurate, as it is possible that G-d who is merciful has forgiven the sins and retracted from his prophetic doomsday prediction. We saw this regarding the city of Ninvei, in which the prophecy of doom was later retracted due to their repentance.
Inaccuracies in predictions of good and blessing: If a prophet predicts a certain good and blessing to occur and it does not happen, then he is certainly a false prophet, as G-d does not retract from His good promises.
Testing the prophet with positive predictions of blessing: Accordingly, when coming to test the eligibility of an acclaimed prophet, he must be tested by stating predictions of positivity and blessing that will occur in the future, and only if they come true can he be verified as a true prophet.

If an already authenticated prophet testified regarding another individual that he is a prophet, then he is considered to be a prophet and is not required to have any future predictions verified prior to his validation.
This was done with Moshe and his student Yehoshua, who Moshe testified to be a prophet and thereby he was not asked to perform any miracles.
Not to test a prophet too much: An authenticated prophet must be believed and cannot be tested too many times out of doubt of his authenticity.