The religious leaders of Israel were upset. They were grumbling and criticizing. What had them so disgruntled? "This man (Jesus) receives sinners and eats with them" (Luke 15:2).
They were angry that the outcasts and rejects, the notorious sinners of Israel, were coming to Jesus "to hear him" (v1) and that Jesus actually "received them." There are two things to point out here.
First of all, the sinners who were coming to hear Jesus were doing exactly what all of Israel were supposed to be doing! Way back in Exodus when God shouted his 10 commandments to Israel from the top of Mt. Sinai, Israel responded by asking God never to speak to them (directly) again, or they would die. Instead, they said they needed a mediator to speak to them for God (Ex 20:18-21). And this was God's plan all along. When they asked God to not speak to them anymore, God told Moses, 'They are right in what they have spoken' (Deut 18:17). 'They are right, they WILL die if I speak to them in my holiness. They DO need a mediator; someone to speak to them for me.' So God promised to send them just that. He said that he would send them a Prophet, and he would put the words of God in this Prophet's mouth. And whoever did not listen to this Prophet would face serious consequences (Deut 18:15-19).
So Israel was looking for this Prophet to come. And the requirement was that they had to hear him...or face the consequences. So when John the Baptist came with his ministry, they asked him if he was the Prophet (John 1:21). There was an expectation in Israel, all these hundreds of years later, for God to send them this Prophet so they could hear God without dying. John pointed to Jesus and said 'This is the one!' And later, God himself testified about Jesus. When Jesus took Peter, James and John up a mountain and showed them his glory, God spoke up and said, "This is my Son, my Chosen One; listen to him!" (Luke 9:35). Listen to him! That's what was said about the Prophet; they must hear him.
So back to the sinners of Israel coming to Jesus. Jesus had just said (in the last verse of Luke 14) "He who has ears to hear, let him hear." And the sinners were coming to hear him. And the Pharisees were mad.
See the problem? The religious leaders should have been the ones who recognized Jesus as the promised Prophet. They should have told Israel, "This is the Prophet! Listen to what he has to say!" But instead, they have no ears to hear. And they are angry about the sinners coming to hear Jesus and to repent and to enter the kingdom of God.
The second problem with this is that the Pharisees themselves were sinners, they just didn't realize it! They were full of self-righteousness. Instead of being angry that Jesus was receiving sinners, they should have come to him humbly, as sinners, and he would have received THEM.
In response to their grumbling about the repentant sinners, Jesus told a parable with three parts. The most famous is the third part, about the prodigal son. But all three parts have the same theme. Something/Someone is LOST. It is searched for and FOUND. And then there is SHARED JOY.
Let's just look at the first part of the parable. A story of a shepherd who has 100 sheep. One of the sheep is lost. Instead of being happy with the 99, the shepherd leaves them to go and search diligently for the one that is lost. Jesus said, "And when he has found it, he lays it on his shoulders, rejoicing" (15:5). Just as God brought Israel out of Egypt by his own mighty power (not theirs) and bore them on eagles' wings (Ex 19:4), so this picture of the shepherd tells the same story. The sheep has no power, but is carried by the shepherd, who is rejoicing!
We have no power to come to God, but God searches for us while we are in our sins. He finds us and carries us on his back, as it were. Carries us home to himself...rejoicing all the way! God has a different attitude than the Pharisees about sinners repenting. The Pharisees are grumbling, but God is rejoicing.
And it is a shared joy. Jesus says the shepherd returns home and calls his friends and neighbors, saying, "Rejoice with me, for I have found my sheep that was lost." Rejoice WITH ME. Share my joy! Sinners are repenting! They are listening to the Mediator who speaks to man from God.
Jesus said, "Just so, I tell you, there will be more joy in heaven over one sinner who repents than over ninety-nine righteous persons who need no repentance" (v17). JOY IN HEAVEN. What a concept! God is a happy God. Yes, he has holy wrath against sin, but he poured this wrath out on his Son, Jesus, at the cross so that he could rescue his lost sheep! Jesus died as the great Shepherd, laying down his life for his sheep, and he rose from the grave to give us eternal life! God wants his lost sheep found, and when he rescues us, he rejoices.
What about the 'righteous persons who need no repentance'? I think this is aimed at the Pharisees. There are NO righteous persons who need no repentance (Romans 3:9-20). But there are many self-righteous people who think they need no repentance.
By God's grace, let us realize that WE are the lost sheep - the sinners - who must repent and come and hear Jesus. We must believe on him and his death and resurrection.
Finally, let our reaction be like God's. Let us rejoice over repentance!