According to Bible "i tell you the truth, if you have faith as small as a mustard seed, you can say to this mountain, "Move from here to there"and he would listen to you, Matthew 17:20

Some people have faiths and they believe they can move mountain, but, unfortunately, they cant,
I could remember when i traveled to Ibadan, Nigeria. I heard about a man that went to zoo (where tiger was kept) he jumped into the cage and pray that GOD "GOD, GIVE ME POWER TO CONQUER THIS TIGER!!!!, He believed God will certainly give him power as he gives Samson because he has faith (Confidence). The tiger rushed him and tear this man apart,

Why? What happened? I know the man tempted GOD because the bible says, It is written again, You shall not tempt the Lord your God (Matt 4:7)

Now tell me, why must some people receive healing while some will not?
With faith, Mountain can be moved, but some people prayed after having faith, and nothing would happen,

Can somebody tell me something i need to know?

;d

at the tiger guy
I can't wait to see the answers Christians would give

Well, IMO, the answer is that God doesn't answer prayers
Look at it this way.
If I wake up every morning and pray to Nairaland to give me 500 naira, and then later that day someone gives me 400 naira, I'll say nairaland has given me the right amount I need. However if I dont get any money that day, I can say nairaland knows that I dont need the money right now or that possessing such money could be harmful to me. Then maybe two months later, i work my butt off and finally make 600 naira, I'll give a testimony saying "I have been praying to nairaland for two months now for 500 naira, and today he finally provided it -- and even more than I asked for"
However, every sane person should know that nairaland cannot possibly answer my prayers.

Now replace nairaland with God

Now that's just how far coincidence can carry you. If by some sheer piece of luck the tiger in that cage from your story had been fed only a few minutes before the faith-drunken guy hopped in, he might be able to get out alive and testify that he had just witnessed a miracle,

Why can't we? Because we do not have the self belief that is necessary. We have all the tools to do all these socalled miracles, but our lack of belief(or faith) in ourselves, in our latent inner potentials, is the only hinderance that we have. Religious dogmas, science, and our own cultural traditions have made sure that this hindrance stay in place for the last. . . couple of millenia or even longer.

Jesus answered the question in the scripture you quoted. Unbelief is the problem , that is why the message you hear is important. If you expose yourself to messages of faith, you will have your faith strengthened to do supernatural things. I have several personal testimonies of miracles and healing wrought through me and several other people too. As you feed on the word. But if you are hearing messages of umbelief , your faith won't work. Even if you want it to.