hecy.

Reply Obj. 3: The prophecy of the demons can be distinguished from
Divine prophecy by certain, and even outward, signs. Hence Chrysostom
says [*Opus Imperf. in Matth., Hom. xix, falsely ascribed to St. John
Chrysostom] that "some prophesy by the spirit of the devil, such as
diviners, but they may be discerned by the fact that the devil
sometimes utters what is false, the Holy Ghost never." Wherefore it
is written (Deut. 18:21, 22): "If in silent thought thou answer: How
shall I know the word that the Lord hath spoken? Thou shalt have this
sign: Whatsoever that same prophet foretelleth in the name of the
Lord, and it come not to pass, that thing the Lord hath not spoken."
_______________________

SIXTH ARTICLE [II-II, Q. 172, Art. 6]

Whether the Prophets of the Demons Ever Foretell the Truth?

Objection 1: It would seem that the prophets of the demons never
foretell the truth. For Ambrose [*Hilary the Deacon (Ambrosiaster) on
1 Cor. 12:3] says that "Every truth, by whomsoever spoken, is from
the Holy Ghost." Now the prophets of the demons do not speak from the
Holy Ghost, because "there is no concord between Christ and Belial
[*'What concord hath Christ with Belial?']" (2 Cor. 6:15). Therefore
it would seem that they never foretell the truth.

Obj. 2: Further, just as true prophets are inspired by the Spirit of
truth, so the prophets of the demons are inspired by the spirit of
untruth, according to 3 Kings 22:22, "I will go forth, and be a lying
spirit in the mouth of all his prophets." Now the prophets inspired
by the Holy Ghost never speak false, as stated above (Q. 111, A. 6).
Therefore the prophets of the demons never speak truth.

Obj. 3: Further, it is said of the devil (John 8:44) that "when he
speaketh a lie, he speaketh of his own, for the devil is a liar, and
the father thereof," i.e. of lying. Now by inspiring his prophets,
the devil speaks only of his own, for he is not appointed God's
minister to declare the truth, since "light hath no fellowship with
darkness [*Vulg.: 'What fellowship hath light with darkness?']" (2
Cor. 6:14). Therefore the prophets of the demons never foretell the
truth.

_On the contrary,_ A gloss on Num. 22:14, says that "Balaam was a
diviner, for he sometimes foreknew the future by help of the demons
and the magic art." Now he foretold many true things, for instance
that which is to be found in Num. 24:17: "A star shall rise out of
Jacob, and a scepter shall spring up