8......when a man sets out, unseasonably and needlessly, to perform a marvel or a mighty work, apart from the fact that this is tempting God, which is a great sin, it may be that he will not succeed, and will engender in the hearts of men discredit and contempt for the faith. For, although at times such persons may succeed because for other reasons and purposes God so wills it, as in the case of Saul's witch (if it be true that it was indeed Samuel who appeared on that occasion), they will not always so succeed; and, when they do so, they go astray none the less and are blameworthy for having used these graces when it was not fitting.
The second manner in which we may fall away is in ourselves and has respect to the merit of faith; for, if a man make much account of these miracles, he ceases to lean upon the substantial practice of faith, which is an obscure habit; and thus, where signs and witnesses abound, there is less merit in believing. In this way Saint Gregory says that faith has no merit when human reason provides experience. And thus these marvels are never worked by God save when they are really necessary for belief. Therefore, to the end that His disciples should not be without merit, though they had experience of His resurrection, He did many things before He showed Himself to them, so that they should believe Him without seeing Him. To Mary Magdalene, first of all, He showed the empty tomb, and afterwards bade the angels speak to her (for, as Saint Paul says, faith comes by hearing); [646] so that, having heard, she should believe before she saw. And, although she saw Him, it was as an ordinary man, [647] that, by the warmth of His presence, He might completely instruct her in the belief which she lacked. And He first sent to tell His disciples, with the women, and afterwards they went to see the tomb. And, as to those who went to Emmaus, He first of all enkindled their hearts in faith so that they might see Him, dissembling with them as He walked. And finally He reproved them all because they had not believed those who had announced to them His resurrection. And He reproved Saint Thomas because he desired to have the witness of His wounds, by telling him that they who saw Him not and yet believed Him were blessed.
9. And thus it is not the will of God that miracles should be wrought: when He works them, He does so, as it were, because He cannot do otherwise. And for this cause He reproved the Pharisees because they believed not save through signs, saying: Unless ye see marvels and signs, ye believe not.' Those, then, who love to rejoice in these supernatural works lose much in the matter of faith.