(Luke 19:1-10)
In order to finance the Roman Empire, the Romans levied heavy taxes on all the nations under their control. The Jews were opposed to these taxes because much of the money went to support a secular government and its pagan gods. Tax collectors were among the most hated people in Israel. They did not receive any salary for their work but collected as much money as they could so that they would have a handsome profit after paying the government the appointed sum. Jews by birth, they chose to work for Rome. Their fellow Jews considered them to be traitors.
(Life Application Bible, Tyndale House Publishers, Inc. Wheaton, Illinois, and Zondervan Publishing House, Grand Rapids, Michigan, 1845.)

Zacchaeus was not only a tax collector but he was referred to as a "chief tax collector." As a ruler in the Greco-Roman world, Zacchaeus would have enjoyed relative power and privilege. (Green, Joel, ed., The Gospel of Luke, Eerdmans, Grand Rapids, 1997, p. 282.) He held a position of great influence in the political structure of that time. He had been placed at the head of the entire tax district of Jericho and vicinity, one of the main Palestinian tax offices.
(Hendriksen, William. New Testament Commentary, Exposition of the Gospel of Luke, Baker, Grand Rapids, 1978, 247-248.)

The method of collecting taxes was open to wide abuse, which made the populace regard those in the profession with hate and contempt. Some collectors were notorious for extortion. Among them was Zacchaeus.
(Guthrie, Donald, Jesus the Messiah, Zondervan, Grand Rapids, 1972, p. 141.)

No wonder the people muttered when Jesus called to Zacchaeus and went to his house. The crowd's reaction to seeing Jesus and His disciples walking to the home of a chief tax officer was typical. They hated Zacchaeus because he symbolized a system they despised. They did not see him as Jesus did, as a man in need.

When Jesus said: "Today salvation has come to this house," He did not imply that the act of giving to the poor had saved Zacchaeus, but that his lifestyle evidenced his right relationship before God. (Walvoord, John and Roy Zuck, eds. The Bible Knowledge Commentary. Victor Books, USA, 1983, 252.) Because of Zacchaeus' change of heart, manifested by his actions, Jesus called Zacchaeus "a son of Abraham." A true Jew--not only of the lineage of Abraham but one who also walks "in the footsteps" of Abraham's faith (Romans 4:12). (The New International Version Study Bible, Zondervan, Grand Rapids, 1985, p. 1576.)

Zacchaeus, upon seeing and hearing Jesus, repented of his unscrupulous deeds and vowed to give half of his possessions to the poor and to repay anyone he may have cheated four times the amount. He was an immediate convert and his faith was put into practice instantly.
(Oglivie, Lloyd, ed., The Communicator's Commentary, Waco, TX, Word Books, 1983, 271.)

Jesus continued by saying: "For the Son of Man came to seek and to save what was lost." In this statement the word lost does not mean damned or doomed. It simply means "in the wrong place." A man is lost when he has wandered away from God; and he is found when once again he takes his rightful place as an obedient child in the household and the family of his Father.
(Barclay, William, The Gospel of Luke, Westminister, Philadelphia, 1975, 235.)

Roman Rule

According to Roman law, if you defrauded somebody you were to repay them fourfold. He met the law's requirements, but beyond that he proposed to give away half of his goods. That was entirely voluntary.
(Oglivie, Lloyd, ed., The Communicator's Commentary, Waco, TX, Word Books, 1983, 271.)

Hebrew Law and Custom

Zaccheus' fourfold repayment of those he has cheated out of anything was almost the extreme repayment under the law in case of theft. (See Exodus 22:1). (The New International Version Study Bible, p. 1576.)

Digs and Documentary Evidence

New Testament Jericho was excavated in 1950. It was a magnificent Roman-style city, with pools, villas, a hippodrome and a theater. A great civic center, of the best Roman masonry, with a grand facade containing statuary niches, potted plants and a reflecting basin before it, bear witness to the grandeur of the international culture that was Palestine's during the time of Jesus.
(The Zondervan Pictorial Dictionary of the Bible, p. 415.)