This is not a prediction, but an imprecation or curse, as it is called, Judges 9:57, which, being grounded upon just cause, and being the only way by which Jotham could perform the duty of the avenger of his brethren's blood, which was incumbent upon him, had its effect, as others in like case had, as Joshua 6:26, compared with 1 Kings 16:34 2 Kings 2:24.
Related Commentaries of Judges 9:20
Judges 9:20
20 But if not, let fire come out from Abimelech, and devour the men of Shechem, and the house of Millo; and let fire come out from the men of Shechem, and from the house of Millo, and devour Abimelech.