Just as prophecy extends to whatever can be known supernaturally, so the working of miracles extends to all things that can be done supernaturally; the cause whereof is the divine omnipotence which cannot be communicated to any creature. Hence it is impossible for the principle of working miracles to be a quality abiding as a habit in the soul. On the other hand, just as the prophet’s mind is moved by divine inspiration to know something supernaturally, so too is it possible for the mindof the miracle worker to be moved to do something resulting in the miraculous effect which God causes by His power. Sometimes this takes place after prayer, as when Peter raised to life the dead Tabitha (Acts 9:40): sometimes without any previous prayerbeing
— from Summa Theologiae, Question 178. The grace of miracles.