In Mark 11, Jesus curses a fruitless fig tree. The next day Peter comments on the fig tree, noticing that it was now withered. Jesus turns this into a lesson on faith and forgiveness, seemingly unrelated concepts to a withered fig tree. It seems strange that Jesus would use the holy spirit on this fruitless fig tree, but it provided a valuable lesson.
Our salvation seems an impossible task, like a mountain being cast into the sea or a tree withering in a day. Jesus had earlier stated that with God nothing is impossible. It is up to us to believe with all our heart, but that belief must be seen in our actions. In this example, Jesus points out the need for genuine, heartfelt prayer, and also the need to forgive others.
Perhaps James is alluding to some of these ideas when he writes in James 5, “The prayer of a righteous person has great power as it is working”. Prayer is such an amazing and comforting idea, that our prayers can have a positive influence on others.