We all know the story of Zacchaeus the tax collector who climbed upon a sycamore tree to meet Jesus. Jesus asked him to alight and said he will partake of food in house. Zacchaeus became repentant and gave all his portions that he has hoarded to the poor.
As an idiom Zacchaeus means a repentant person who pleases God.
Example: In my encounter with Christ, I became a Zacchaeus.