While He spoke these things to them, behold, a ruler came and worshiped Him, saying, "My daughter has just died, but come and lay Your hand on her and she will live." So Jesus arose and followed him, and so did His disciples. . . . When Jesus came into the ruler's house, and saw the flute players and the noisy crowd wailing, He said to them, "Make room, for the girl is not dead, but sleeping" (Mt 9.18-9, 23-4).
In the face of the one who holds power over life and death, the one who can lay down his life and take it back once more, death becomes like mere sleep. What is naturally irreversible for ordinary persons such as you and me -- to bring a dead person to life again -- for Christ is no more difficult than rousing a little girl from her slumbers.
This is true when speaking of physical death, but it is also true when speaking of spiritual death. Thus Paul tells the Ephesians: And you He made alive, who were dead in trespasses and sins (Eph 2.1). Gregory of Nyssa, rephrasing a golden one-liner from Origen, said it this way: Nothing is impossible for the Omnipotent; no one is incurable for the One who created it.
When we find that we ourselves are sick, not to mention others with whom we have to do, we can pray with confidence to Christ the Healer that he visit and heal our infirmities. Dumitru Stăniloae said: Mercy accompanies Christ every and at all times. That is why we are to ask for it always. But mercy apart from power is good for nothing. The Creator to whom no one is incurable (not even I!) is the same Omnipotent to whom nothing is impossible. With men this is impossible, but with God all things are possible (Mt 19.20).