The fig tree outside of the Temple wasn’t bearing fruit (v.19). Green figs were nasty to eat, so the people would wait to eat them. Carson writes, “That it was not the season for figs explains why Jesus went to this particular tree, which stood out because it was in leaf. Its leaves advertised that it was bearing, but the advertisement was false. Jesus, unable to satisfy his hunger, saw the opportunity of teaching a memorable object lesson and cursed the tree, not because it was not bearing fruit, whether in season or out, but because it made a show of life that promised fruit yet was bearing none.” Lane adds, “Just as the leaves of the tree concealed the fact that there was no fruit to enjoy, so the magnificence of the Temple and its ceremony conceals the fact that Israel has not brought forth the fruit of righteousness demanded by God.”
In other words, the fig tree serves as a symbol for hypocrisy—whether in the Jewish temple or otherwise. Israel is often associated with a fig tree (e.g. Jer. 8:13; 29:17; Hos. 9:10, 16; Joel 1:7; Micah 7:1-6), and the destruction of the fig tree is associated with judgment (Hos. 2:12; Isa. 34:4; cf. Lk. 13:6-9).
 Carson, D. A. Matthew. In F. E. Gaebelein (Ed.), The Expositor’s Bible Commentary: Matthew, Mark, Luke (Vol. 8). Grand Rapids, MI: Zondervan Publishing House. 1984. 445.
 Lane, W. L. (1974). The Gospel of Mark (p. 400). Grand Rapids, MI: Wm. B. Eerdmans Publishing Co.