The manifold wisdom of God grants with manifold and inscrutable kindness salvation to men; and imparts to each one according to his capacity the grace of His bounty, so that He wills to grant His healing not according to the uniform power of His Majesty but according to the measure of the faith in which He finds each one, or as He Himself has imparted it to each one.
For when one believed that for the cure of his leprosy the will of Christ alone was sufficient He healed him by the simple consent of His will, saying: “I will, be thou clean.” When another prayed that He would come and raise his dead daughter by laying His hands on her, He entered his house as he had hoped, and granted what was asked of Him. When another believed that what was essential for his salvation depended on His command, and answered: “Speak the word only, and my servant shall be healed,” He restored to their former strength the limbs that were relaxed, by the power of a word, saying: “Go thy way, and as thou hast believed so be it unto thee.” To others hoping for restoration from the touch of His hem, He granted rich gifts of healing. To some, when asked, He bestowed remedies for their diseases. To others He afforded the means of healing unasked: others He urged on to hope, saying: “Willest thou to be made whole?” to others when they were without hope He brought help spontaneously. The desires of some He searched out before satisfying their wants, saying: “What will ye that I should do for you?” To another who knew not the way to obtain what he desired, He showed it in His kindness, saying: “If thou believest thou shalt see the glory of God.” Among some so richly did He pour forth the mighty works of His cures that of them the Evangelist says: “And He healed all their sick.” But among others the unfathomable depth of Christ’s beneficence was so stopped up, that it was said: “And Jesus could do there no mighty works because of their unbelief.”
And so the bounty of God is actually shaped according to the capacity of man’s faith, so that to one it is said: “According to thy faith be it unto thee:” and to another: “Go thy way, and as thou hast believed so be it unto thee;” to another “Be it unto thee according as thou wilt,” and again to another: “Thy faith hath made thee whole.”
~ St. John Cassian: Conference of Abbot Chæremon. on the protection of God