What is the context?
Returning to the city in the morning, Jesus is hungry. He approaches a fig tree but finds only leaves. He declares that it will never bear fruit again, and it withers. The disciples are amazed and ask how this happened so quickly.
Jesus responds by teaching about faith without doubt, a mountain being lifted into the sea, and believing prayer. The disciples' attention to the tree's sudden withering becomes an opportunity to teach them about trusting God's power.
The surrounding chapter repeatedly raises the question of fruit: the tree has none, one son actually goes to work, and the vineyard's tenants refuse the owner his harvest. Mark 11:12–25 gives the related fig-tree account around the temple scene, with the disciples seeing the withered tree the next morning. In Mark, Jesus expressly directs their faith toward God.
How is this passage commonly understood?
Christians commonly read the fruitless tree as a warning about a life that does not bear the fruit God seeks, alongside a lesson in trusting Him in prayer. Wesley on 21:20–21 draws out both fruitfulness and faith; the US Catholic bishops' note on 21:18–22 understands the act as a warning of judgment on fruitlessness and an example of the power of believing prayer.
Where does this fit in God's plan?
The fruit God seeks comes through a living relationship with Christ. John 15:1–8 describes Him as the vine and His followers as branches. Remaining in Him leads to fruit that glorifies the Father. The warning about barrenness belongs beside that positive purpose: God forms people whose lives bear fruit through His Son.
Prayer is part of that relationship. John 15 joins remaining in Jesus and His words with asking, and 1 John 5:14–15 describes confidence in asking according to God's will. The larger picture brings faith, prayer, and fruitful life together around Him.
What is our position?
Prayer and Faith discusses Mark's account of this same fig-tree event. It reads the act as a warning that Israel's outward religious life was not bearing the fruit God sought, and that judgment was coming. The study understands the mountain-moving teaching as faith working in line with God's purposes.
The study therefore reads believing prayer as trust in God and what He purposes to do. It does not treat confidence in a desired result as a way to make that result happen. Its fuller explanation appears in Prayer and Faith.