Cyril of Alexandria

Zacchaeus was chief of the publicans, a man entirely abandoned to covetousness, and whose sole object was the increase of his gains: for such was the practice of the publicans, though Paul calls it "idolatry," possibly as being fit only for those who have no knowledge of God. But Zacchaeus continued not among their number, but was counted worthy of mercy at Christ's hands: for He it is Who calls near those who are afar off, and gives light to those who are in darkness. …

Commentary on the Gospel of Luke, Sermon 127 ↗

Ambrose of Milan

"And, behold, there was a man named Zacchaeus." Zacchaeus in the sycamore; the blind man by the wayside. The Lord waits for the one to have mercy on him and honors the other with the radiance of his visit. He questions the one before healing him and attends the other's house as an uninvited guest. He knew that his host's reward was to be rich. Although Christ had not yet heard his voice of invitation, he has heard his good will.

Commentary on Luke ↗

Bede

And entering, he was passing through Jericho; and behold, a man named Zacchaeus, who was a chief tax collector, and he was rich. And he was seeking to see Jesus, who he was, and he could not because of the crowd, for he was of short stature. And running ahead, he climbed up into a sycamore tree to see him, because he was to pass that way. What is impossible with men is possible with God (Luke XVIII). …

On the Gospel of Luke ↗

Bonaventure

Second, he refutes tenacity in possessing by approving a twofold liberality. And having entered, he was passing through Jericho, etc. Above he refuted cupidity by approving poverty; here, second, he refutes tenacity by approving liberality. And since the dispersal and sharing of temporal goods is the way to the multiplication of spiritual goods, therefore in this part he first approves the liberality that distributes temporal goods; second, the diligence in multiplying spiritual goods, at the passage: As they were hearing these …

Commentary on Luke, Chapter 19 ↗