Paul speaks of Timothy learning the faith in God from his mother and grandmother but says he should listen to the Spirit and act accordingly, despite possible dangers.  He urges him to have no fear as long as he is obedient.  In Luke, Jesus tells his disciples that faith the size of a grain of mustard is enough to see mountains move.  He then goes on to tell them not to expect God to praise them for doing as God has commanded, but to obey out of love for God.

Faith is defined by our obedience.