What does Mark 11:20 mean?

Jesus and the disciples spent the night on the Mount of Olives (Luke 21:37–38), most likely in or near Bethany, two miles, or three kilometers, east of Jerusalem. The day before, they passed a fig tree which Jesus cursed because it had no figs. Now, they discover the tree is utterly ruined. Matthew says the tree became withered "at once" (Matthew 21:19), while Mark specifies the disciples don't notice until the next morning. Considering it is a full-grown fig tree in leaf, twenty-four hours for it to completely wither is "at once," and as much a miracle as it happening in one second. Most likely, the tree died right away, and by the next morning its roots were withered as well.

The thoroughness of the destruction is consistent with Jesus' other miracles. When He feeds a crowd of thousands, they leave satisfied, not merely tided over, and with leftovers for the disciples (Mark 6:32–44; 8:1–10). When He makes wine, it is immediately recognized for being exceptionally good (John 2:1–11). When He heals the blind, sight is returned completely (Mark 8:22–26). And when He heals a deaf man, the witnessing crowd declares, "He has done all things well" (Mark 7:31–37). It should be no surprise that when Jesus tells a tree it will never provide fruit for people to eat again, the tree withers to the roots.

Fig trees are often a symbol for Israel in the Old Testament, especially when God is warning about coming judgment (Jeremiah 8:13; Hosea 9:10; Micah 7:1–7). It's possible that as the disciples look at the fig tree, they remember the withered grass of Psalm 90:6, the languishing fig tree in Joel 1:12, and Hosea 9:16 which talks about Ephraim's root drying up. The tree will never bear fruit again. In the same way, the temple will never offer communion with God again.