Luke 19:4

And he ran. Mystically, the sycamore is the cross of Christ and His doctrine, which to the Gentiles and men of this world is mere folly, but to Zacchæus and the faithful is the wisdom of God, and the power of God. 1 Cor. i. 24. S. Gregory, lib. xxvii. Moral.: in fine, "Let us leave the wisdom that is hurtful, that we may gain that which is to our profit, &c. The dwarf Zacchæus submitted himself to the sycamore tree and saw the Lord; for they who choose humbly the folly of the world, these wisely contemplate the wisdom of God. A multitude hinders our slowness to see God, for the tumults of worldly cares so press upon the infirmity of the human mind that it cannot contemplate the light of truth. We are wise to ascend the sycamore if we retain in our minds, with forethought, that foolishness which is received from God."

Theophylact speaks as follows: "We climb the fig-tree; that is, we ascend above the allurements of pleasure, which is signified by the fig-tree we mount up by Penitence, but we come down through Humility."