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.
Matthew Henry
Concise Bible Commentary
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.
SDA Bible Commentary (limited)
Volume 1-7
25. I have dreamed. The common claim of false prophets. The repetition of the phrase is for emphasis.