The man first tried the apostles to see if they could heal his son, but they could not do it. This really saddened Jesus.
When I read that I thought about myself. I am sent to this earth to be an instrument of Jesus Christ and to do His will as He is not here. He expects me to be prepared and ready to "heal" His children as they need it. We truly are His hands on the earth.
When He hears the apostles couldn't heal the boy, He says:
"O faithless generation, how long shall I be with you? How long shall I suffer you?"
And I hear that has Him saying:
"Ashley. I have taught you. We have communed with each other. You have a solid testimony of the gospel -- yet you keep your gifts to yourself. I gave you gifts so you could be there for others when I am not there, yet my children are leaving your presence unhealed. How long will this go on?"
I feel like I have so much potential but have been useless to the Lord lately. It is all about preparation -- being ready at all times to serve.
In verses 28 & 29, the apostles ask -- why couldn't we heal the man? And Jesus relies, "This kind can come forth by nothings, but by prayer and fasting."
Christ was prepared and the apostles were not. They both held the same priesthood powers, but one could employ them and the other could not.