The Torah in Parashat Shoftim (Debarim 18:20) commands that if somebody delivers a message which he falsely claims was communicated to him prophetically by G-d, he must be put to death. The Gemara interprets this warning as introducing a prohibition against not only speaking false prophecy, but also relaying a true prophetic message, delivered by a prophet, as though one heard it directly from G-d. Meaning, if a person heard a prophet deliver a prophetic message, and this person then speaks those words to others claiming that they were prophetically communicated to him, then he is in violation of this Biblical command.
The Sefer Ha’hinuch explains that the Torah issued this prohibition because of the special importance of prophecy, which constitutes one of the important foundations of our faith – that G-d communicates His messages to prophets. If imposters falsely claim to have received prophecy, and their predictions are not fulfilled, people will lose respect for the institution of prophecy, and will question the validity of even authentic prophets. And if a person relays a prophet’s words as though they had been spoken to Him, people will regard him as a prophet and spiritual guide. They will then treat all his words as binding and follow his example, when in truth he might not be worthy of such esteem and emulation. As a result, the people will be led astray by following the directives and example of somebody who should not be looked to as a mentor.
This command applies in all times and places, and is binding upon both men and women. One who conveys a message which he falsely claims to have received through prophecy is put to death. There is a general rule that whenever the Torah assigns the death penalty for a violation, without specifying which form of execution should be administered, it refers to Henek (strangulation). Hence, the punishment for delivering false prophecy is Henek.
The contemporary application of this prohibition is that those who speak or publish words of Torah must exercise extreme care to share only what is true. Nowadays, we do not have prophets, but we instead have teachers of Torah who deliver the word of G-d as expressed in the Torah, and they must ensure to relay the Torah accurately, without distortions that could mislead the people.