Sometimes a prophecy’s message is for the prophet himself, and at other times for others, who are commanded to heed his instructions. There is no obligation to heed just anyone who shows a wondrous sign and says words; we are only obligated to heed one who we recognize as fit for prophecy.

A prophecy might be for the prophet himself, to expand his mind and to increase his knowledge, so he knows of lofty matters he hasn’t known about previously. A prophet could also be sent to one of the world’s nations or to the people of a city or kingdom, to prepare them for the future and to tell them what to do, or to stop them from doing evil. When the prophet is sent, he is given a sign or wonder [to perform before them], so the listeners will know that God truly sent him. Not everyone who performs a sign or wonder is to be believed to be a prophet. Rather, [this is how we identify a true prophet]: If he is a person we previously knew to be fitting for prophecy through his wisdom and actions that are superior to that of his contemporaries, and if he follows the ways of prophecy, its holiness and asceticism, and he then proceeds to perform a sign and wonder and says that God sent him, it is a mitzva to heed him. This is stated in the verse: “[A prophet from your midst, from your brethren, like me, the Lord your God will establish for you;] him you shall heed” (Deuteronomy 18:15). (Rambam, Mishneh Torah, Hilkhot Yesodei HaTorah 7:7)