Faith (even weak faith) helps us with life's trials--if it is right faith.
Jesus returned to the Apostles after a brief separation (see: From the Mountain to the Valley) and walked into a commotion. The Apostles were surrounded by a crowd and arguing with teachers of the law.
A man from the crowd explained that the Apostles were unable to cast a demon out of his son. Their power failure fueled the fire for these teachers of the law. They had a chance to to turn the crowd against Christ's followers.
The Apostles were baffled. Jesus had recently given them the power and authority over demons when he sent them out into the towns and villages. They successfully drove out demons from people. They had the power but they could not drive the demon from this boy.
Jesus declared them to be a faithless generation. The Apostles had some faith but they did not fully understand the true nature of Jesus' and his power. Like some church goers their faith was limited by an incomplete understanding of what it means to follow Jesus.
The Apostles (and some church-goers today) had a self-centered faith. They liked to be around Jesus and hear him teach. They liked the miracles and the possibility of becoming important but the idea of servant hood and sacrifice were not on their agenda.
The boy's father had a faltering faith. He believed in what Jesus was able to do, but struggled with doubt. Jesus said, "Everything is possible for him who believes."
Faith is an active force in the accomplishment of miracles. Jesus said, "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 it will move. Nothing will be impossible for you." (Matthew 17:20)
The father's faith was mixed with doubt. "I do believe; help me in my unbelief," he said.
Jesus' response to this man's imperfect faith was to cast the demon out of his son. It is encouraging that our faith does not need to be perfect. On the other hand, our reliance on God must be complete.
Unbelief has no power. It can block miracles: “And so he did only a few miracles there because of their unbelief.” (Matthew 13:58)
Unbelief can bring discouragement among God’s people: “But the other men who had explored the land with him answered, 'We can’t go up against them! They are stronger than we are!' So they spread discouraging reports about the land among the Israelites.” (Numbers 13:31-32)
Power comes to the people of God when there is faith. Jesus told the woman with the issue of blood, “Your faith has made you whole.”
“...all things are possible to him who believes.” (Mark 9:23)