Mark 9

Jesus heals! Peter, James and John saw Jesus transfigured before them. They saw the power of God manifested. If we can believe in the impossible, have faith in His power, nothing will be impossible. Jesus Christ is God.
He has been given the keys to life and death. In Him is life, abundantly more than we can hope for. If you cannot understand the depth of the Father's love and have problems trusting that you can be loved like that, ask Him and He will help you with your lack of faith.
Place your trust in Jesus. He can heal you physically, mentally and spiritually. Don't be afraid to ask Him for help. The biggest enemy of our souls is fear. The only thing that we have to fear is fear itself. It paralyzes us into doing nothing. Perfect love cast out fear.
Jesus is the perfect love of God who died for us and rose again, to save those who put their faith in Him.

And He said to them, "Assuredly, I say to you that there are some standing here who will not taste death till they see the kingdom of God present with power."

2 Now
after six days Jesus took Peter, James, and John, and led them up on a high mountain apart by themselves; and He was transfigured before them. 3 His clothes became shining, exceedingly white, like snow, such as no launderer on earth can whiten them. 4 And Elijah appeared to them with Moses, and they were talking with Jesus. 5 Then Peter answered and said to Jesus, "Rabbi, it is good for us to be here; and let us make three tabernacles: one for You, one for Moses, and one for Elijah"— 6 because he did not know what to say, for they were greatly afraid.

7 And a cloud came and overshadowed them; and a voice came out of the cloud, saying, "This is My beloved Son. Hear Him!" 8 Suddenly, when they had looked around, they saw no one anymore, but only Jesus with themselves.

9 Now as they came down from the mountain, He commanded them that they should tell no one the things they had seen, till the Son of Man had risen from the dead. 10 So they kept this word to themselves, questioning what the rising from the dead meant.

11 And they asked Him, saying, "Why do the scribes say that Elijah must come first?"

12 Then He answered and told them, "Indeed, Elijah is coming first and restores all things. And how is it written concerning the Son of Man, that He must suffer many things and be treated with contempt? 13 But I say to you that Elijah has also come, and they did to him whatever they wished, as it is written of him."

14 And when He came to the disciples, He saw a great multitude around them, and scribes disputing with them. 15 Immediately, when they saw Him, all the people were greatly amazed, and running to Him, greeted Him. 16 And He asked the scribes, "What are you discussing with them?"

17 Then one of the crowd answered and said, "Teacher, I brought You my son, who has a mute spirit. 18 And wherever it seizes him, it throws him down; he foams at the mouth, gnashes his teeth, and becomes rigid. So I spoke to Your disciples, that they should cast it out, but they could not."

19 He answered him and said, "O faithless generation, how long shall I be with you? How long shall I bear with you? Bring him to Me." 20 Then they brought him to Him. And when he saw Him, immediately the spirit convulsed him, and he fell on the ground and wallowed, foaming at the mouth.

21 So He asked his father, "How long has this been happening to him?"

And he said, "From childhood. 22 And often he has thrown him both into the fire and into the water to destroy him. But if You can do anything, have compassion on us and help us."

23 Jesus said to him, "If you can believe, all things are possible to him who believes."

24 Immediately the father of the child cried out and said with tears, "Lord, I believe; help my unbelief!"

25 When Jesus saw that the people came running together, He rebuked the unclean spirit, saying to it, "Deaf and dumb spirit, I command you, come out of him and enter him no more!" 26 Then the spirit cried out, convulsed him greatly, and came out of him. And he became as one dead, so that many said, "He is dead." 27 But Jesus took him by the hand and lifted him up, and he arose.

The NKJV
Study Bible says this: Jesus' transfiguration deeply affected John and Peter, who mention it in their writings. Moses was the lawgiver and liberator, while Elijah was the first of the great prophets. Their presence confirmed the reality that Jesus is the Messiah of Peter's confession. The voice of God the Father was heard audibly three times during the life of Christ. John was not a reincarnation of Elijah, but one who ministered "in the spirit and power of Elijah" in preparing the way for Christ. They did to him whatever they wished refers to the ruthless way John the Baptist was imprisoned and murdered. I believe; help my unbelief expresses the dilemma that even those who believe can be nagged by doubt and hopelessness. Jesus tells plainly of His coming death and resurrection.