Objection 1. It would seem that the wicked cannot work miracles. For miracles are wrought through prayer, as stated above (1, ad 1). Now the prayer of a sinner is not granted, according to John 9:31, "We know that God doth not hear sinners," and Proverbs 28:9, "He that turneth away his ear from hearing the law, his prayer shall be an abomination." Therefore it would seem that the wicked cannot work miracles.
Objection 2. Further, miracles are ascribed to faith, according to Matthew 17:19, "If you have faith as a grain of mustard seed you shall say to this mountain: Remove from hence hither, and it shall remove." Now "faith without works is dead," according to (James 2:20), so that, seemingly, it is devoid of its proper operation. Therefore it would seem that the wicked, since they do not good works, cannot work miracles.
Objection 3. Further, miracles are divine attestations, according to Hebrews 2:4, "God also bearing them witness by signs and wonders and divers miracles": wherefore in the Church the canonization of certain persons is based on the attestation of miracles. Now God cannot bear witness to a falsehood. Therefore it would seem that wicked men cannot work miracles.
Objection 4. Further, the good are more closely united to God than the wicked. But the good do not all work miracles. Much less therefore do the wicked.
On the contrary, The Apostle says (1 Corinthians 13:2): "If I should have all faith, so that I could remove mountains, and have not charity, I am nothing." Now whosoever has not charity is wicked, because "this gift alone of the Holy Ghost distinguishes the children of the kingdom from the children of perdition," as Augustine says (De Trin. xv, 18). Therefore it would seem that even the wicked can work miracles.
I answer that, Some miracles are not true but imaginary deeds, because they delude man by the appearance of that which is not; while others are true deeds, yet they have not the character of a true miracle, because they are done by the power of some natural cause. Both of these can be done by the demons, as stated above (1, ad 2).
True miracles cannot be wrought save by the power of God, because God works them for man's benefit, and this in two ways: in one way for the confirmation of truth declared, in another way in proof of a person's holiness, which God desires to propose as an example of virtue. On the first way miracles can be wrought by any one who preaches the true faith and calls upon Christ's name, as even the wicked do sometimes. On this way even the wicked can work miracles. Hence Jerome commenting on Matthew 7:22, "Have not we prophesied in Thy name?" says: "Sometimes prophesying, the working of miracles, and the casting out of demons are accorded not to the merit of those who do these things, but to the invoking of Christ's name, that men may honor God, by invoking Whom such great miracles are wrought."
In the second way miracles are not wrought except by the saints, since it is in proof of their holiness that miracles are wrought during their lifetime or after death, either by themselves or by others. For we read (Acts 19:11-12) that "God wrought by the hand of Paul... miracles" and "even there were brought from his body to the sick, handkerchiefs... and the diseases departed from them." On this way indeed there is nothing to prevent a sinner from working miracles by invoking a saint; but the miracle is ascribed not to him, but to the one in proof of whose holiness such things are done.
Reply to Objection 1. As stated above (Question 83, Article 16) when we were treating of prayer, the prayer of impetration relies not on merit but on God's mercy, which extends even to the wicked, wherefore the prayers even of sinners are sometimes granted by God. Hence Augustine says (Tract. xliv in Joan.) that "the blind man spoke these words before he was anointed," that is, before he was perfectly enlightened; "since God does hear sinners." When it is said that the prayer of one who hears not the law is an abomination, this must be understood so far as the sinner's merit is concerned; yet it is sometimes granted, either for the spiritual welfare of the one who prays--as the publican was heard (Luke 18:1)4)--or for the good of others and for God's glory.
Reply to Objection 2. Faith without works is said to be dead, as regards the believer, who lives not, by faith, with the life of grace. But nothing hinders a living thing from working through a dead instrument, as a man through a stick. It is thus that God works while employing instrumentally the faith of a sinner.
Reply to Objection 3. Miracles are always true witnesses to the purpose for which they are wrought. Hence wicked men who teach a false doctrine never work true miracles in confirmation of their teaching, although sometimes they may do so in praise of Christ's name which they invoke, and by the power of the sacraments which they administer. If they teach a true doctrine, sometimes they work true miracles as confirming their teaching, but not as an attestation of holiness. Hence Augustine says (QQ. lxxxiii, qu. 79): "Magicians work miracles in one way, good Christians in another, wicked Christians in another. Magicians by private compact with the demons, good Christians by their manifest righteousness, evil Christians by the outward signs of righteousness."
Reply to Objection 4. As Augustine says (QQ. lxxxiii, qu. 79), "the reason why these are not granted to all holy men is lest by a most baneful error the weak be deceived into thinking such deeds to imply greater gifts than the deeds of righteousness whereby eternal life is obtained."
Source: Summa Theologica (New Advent)