In Deuteronomy 13:1 "a dreamer of dreams" is used in a bad sense, and with reason. God communicating His will by dreams was a thing too easy to counterfeit for it not to be misused.

I have heard what the prophets said, that prophesy lies in my name,.... Or, "I hear what the prophets say" (g), &c. though they thought God was at a distance from them, in the highest heavens, and neither saw, nor heard, nor took any notice of what was done on earth, they were greatly mistaken; he heard and observed with indignation the false doctrines and lying prophecies which they delivered out in his name to the people, whether in public or in private; for he is the Lord God omniscient and omnipresent; and therefore, though they deceived the people, they could not deceive him; who knew all their schemes and all their designs, from what principles they acted, and with what views;

saying, I have dreamed, I have dreamed; not a common dream, but a divine dream; this was one way in which the Lord formerly made known his mind and will to his servants, Numbers 12:6; wherefore these false prophets, in imitation of the true ones, and in order to gain credit from the people, pretended they had a dream from the Lord, in which such and such things were revealed to them; and this is repeated by them for the greater certainty of it, and to raise the people's attention as to something very uncommon and extraordinary. So the Targum,

"saying, a word of prophecy has been shown to me in a dream.''

Now, though the people could not contradict them, or know any otherwise than as they might observe that they agreed not with the word of God, or with his will, as made known by the true prophets of the Lord; for if a man says he has dreamed so and so, another cannot say he has not; because no man knows the things of a man, save the spirit of a man that is in him; yet God, that knows all things, knew that these were all lies and impostures, and that they had never had a dream from him, or any revelation of his will in that way.

(g) "dicunt", Calvin, Cocceius.

I have heard what the prophets said, that prophesy lies in my name, saying, I {t} have dreamed, I have dreamed.

(t) I have a prophecy revealed to me as in Nu 12:6.

25. dreamed-I have received a prophetic communication by dream (Nu 12:6; De 13:1, &c. Joe 2:28).

23:23-32 Men cannot be hidden from God's all-seeing eye. Will they never see what judgments they prepare for themselves? Let them consider what a vast difference there is between these prophecies and those delivered by the true prophets of the Lord. Let them not call their foolish dreams Divine oracles. The promises of peace these prophets make are no more to be compared to God's promises than chaff to wheat. The unhumbled heart of man is like a rock; if not melted by the word of God as a fire, it will be broken to pieces by it as a hammer. How can they be long safe, or at all easy, who have a God of almighty power against them? The word of God is no smooth, lulling, deceitful message. And by its faithfulness it may certainly be distinguished from false doctrines.