First Reading: Deuteronomy 18:15-20
The Announcement of a Great Prophet
15 YHWH your God will raise up to you a prophet from the midst of you, of your brothers, like me. You shall listen to him. 16 This is according to all that you desired of YHWH your God in Horeb in the day of the assembly, saying, “Let me not hear again the voice of YHWH my God, neither let me see this great fire any more, that I not die.”
17 YHWH said to me, “They have well said that which they have spoken. 18 I will raise them up a prophet from among their brothers, like you; and I will put my words in his mouth, and he shall speak to them all that I shall command him. 19 It shall happen, that whoever will not listen to my words which he shall speak in my name, I will require it of him. 20 But the prophet, who shall speak a word presumptuously in my name, which I have not commanded him to speak, or who shall speak in the name of other gods, that same prophet shall die.”
World English Bible
[15-20] The book of Deuteronomy was "discovered' during the reign of King Josiah. Even before King Josiah was on the throne, the nation of Judah was reduced to the city-state of Jerusalem; the great powers of the time (Egypt and Babylon) treated Judah as a vassal state or as a no-man's land. With Jerusalem endangered of being conquered, there was a push to put the Law and the traditions of the Temple priests on paper. The book not only preserved the Law and traditions; the religious ethic of compassion and the collective wisdom of the nation's rulers were presented.
 While the book saw a great prophet arising; the caveats below actually discouraged the prophetic tradition. Prophets were usually lower class, self-appointed critics of the religious hierarchy. Prophets always gain the wrath of the ruling bureaucracy. As Jesus commented, religious leaders erect monuments to prophets whom the ancestors of the leaders killed. Deuteronomy recognizes the power of the prophetic tradition, but raises the stakes by justifying the murder of the unpopular prophet (see 18:20)
[16 & 18] Who is the great leader foretold? If the authors of Deuteronomy were bureaucrats, their vote would be for the king, a leader appointed by God to speak for God. The prophet king was a tradition that started with King David as the inspiration for the psalms. Even Jesus referred to King David as a prophet. During the Babylonian exile and afterwards, people desired the charismatic leader who had aspects of king and prophet.
[19-20] There are two caveats: one against the revolutionary and one against the false prophet. The disobedient person who did not listen to God's words, also did not obey his Word found in the Law. This person was an outlaw, an anarchist. By definition, he should die.
The second warning was against the false prophet who spoke in God's name or in the name of idols. This person set himself against the religious leaders. If the religious leaders spoke for the Law, then the prophet critical of the leaders stood outside the religious institution. He was no better than the anarchist; he, too, should die. But, what happened when there was no religious institution (as in the Babylonian exile)?
Do you seek prophetic voices, messages from God to guide your life? Where do you find such voices? What is the cost of following a prophetic voice?