Zacchaeus the Tax Collector

Jesus entered Jericho and was passing through. A man was there by the name of Zacchaeus; he was a chief tax collector and was wealthy. He wanted to see who Jesus was, but because he was short he could not see over the crowd. So he ran ahead and climbed a sycamore-fig tree to see him, since Jesus was coming that way. When Jesus reached the spot, he looked up and said to him: "Zacchaeus, hurry and come down, for I must stay at your house today." So he came down at once and welcomed him gladly. All the people saw this and began to mutter: "He has gone in to be the guest of a man who is a sinner." But Zacchaeus stood up and said to the Lord: "Behold, Lord, the half of my goods I give to the poor. And if I have defrauded anyone of anything, I restore it fourfold." Jesus said to him: "Today salvation has come to this house, since he also is a son of Abraham. For the Son of Man came to seek and to save the lost."

Zacchaeus was a chief tax collector and was wealthy. A tax collector collected taxes for the Roman government that occupied their country. This government required a sum of money and the excess money went to the tax collector. A tax collector
essentially made his money by overtaxing people. He could basically set the amount that people would pay in taxes. This made tax collectors very unpopular among the Jewish people.

When Jesus told him that he wanted to visit his house, he immediately came down and welcomed Jesus with joy. There is a selection of Jesus, but also a free will in the sense that Zacchaeus joyfully welcomed the Lord, see The Predestination Theory.

Zacchaeus promised to give half of his goods to the poor and if he had defrauded anyone to restore it fourfold. This answer is completely in line with what biblical repentance is all about. Real genuine Biblical repentance many times involves certain actions that are done voluntarily without anyone demanding it. In this case it involved giving money, but it can also be something else. Godly sorrow produces repentance (change of mind) while worldly sorrow doesn't, see Godly sorrow and Repent in Salvation.

The reason Jesus said that Zacchaeus was a son of Abraham was because he believed and trusted in Jesus (Rom 9:7–8, Gal 3:5–7). The Son of Man came to
seek and save the lost (Luk 19:10).

Jesus knows what is in people's hearts. He always tells an individual what he
needs to hear, which isn't necessarily what he wants to hear (itching ears).
That is why Jesus says different things to different people:

• Zacchaeus was considered a sinner, and not many people wanted to be associated with him (Luk 19:7), but Jesus said that he wanted to visit him.
• Another rich man thought he was good enough to keep the Mosaic Laws. Jesus showed him that he couldn't, see Jesus and the Young Rich Man.
  No one can (Rom 3:20–24).
• Jesus told a woman from Samaria that he could fill her emptiness with living water, see Jesus and the Woman of Samaria.
• See Jesus the Bread of Life.

Sometimes Jesus asks people in such a way that they recognize their area of ​​need and express it, even though Jesus knows the answer. Jesus wants us to do that.
To confess our need for him (Mat 20:32, Mark 10:51, Luk 18:41, John 5:6). 

Many people took Jesus at his word, they believed, faith can move mountains, see time 9:37–11:58 in John 5 (Part 1) 1–18 • The Heart of Legalism.

Jesus also asked questions to test people, see (John 6:5–7) time 5:59–16:27
in John 6 (Part 1) :1-15 • When you're facing the Impossible. 

Jesu also asked questions to people who were planning how to trap him in his words, see (Mat 21:24–27, Mark 11:29–33, Luk 20:3–8) Jesus' Authority is Challenged
in Jesus' Last Days before his Crucifixion.

See also Some stories in the gospels at the bottom of The Four Gospels.