And if thou say in thine heart, How shall we know the word which the LORD has not spoken? When a prophet speaks in the name of the LORD, if the thing does not follow nor come to pass, it is a word which the LORD has not spoken, but the prophet has spoken it presumptuously; thou shalt not be afraid of him.

The prophets that have been before me and before thee of old prophesied both against many countries, and against great kingdoms, of war, and of evil, and of pestilence. The prophet which prophesied of peace, when the word of the prophet should come to pass, then shall the prophet be known, that the LORD has truly sent him.

Thou shalt speak unto them like this, Thus hath the Lord GOD said; As I live, surely those that are in those wastes shall fall by the sword, and he that is in the open field I will give to the beasts to be devoured, and those that are in the forts and in the caves shall die of the pestilence. For I will make the land into desert and solitude, and the pride of her strength shall cease; and the mountains of Israel shall be desolate, that no one shall pass through. Then they shall know that I am the LORD, when I have made the land into solitude and desert because of all their abominations which they have committed. read more.
And thou, son of man, the sons of thy people are still talking against thee by the walls and in the doors of the houses and speak one to another, each one to his brother, saying, Come, I pray you, and hear what is the word that comes forth from the LORD. And they shall come unto thee as the people come, and they shall be before thee, my people, and they shall hear thy words, but they shall not do them; for with their mouth they flatter, but their heart goes after their covetousness. And, behold, thou art unto them as a singer of love songs, one that has a good voice and can sing well: and they shall hear thy words, but they will not do them. But when this comes to pass (behold, it comes), then they shall know that a prophet has been among them.