1-2 Now the tax collectors and sinners were all gathering round to hear Jesus.  But the Pharisees and the teachers of the law muttered, ‘This man welcomes sinners, and eats with them.’ 3-6 Then Jesus told them this parable: ‘Suppose one of you has a hundred sheep and loses one of them. Doesn’t he leave the ninety-nine in the open country and go after the lost sheep until he finds it? And when he finds it, he joyfully puts it on his shoulders and goes home. Then he calls his friends and neighbours together and says, “Rejoice with me; I have found my lost sheep.” 7 I tell you that in the same way there will be more rejoicing in heaven over one sinner who repents than over ninety-nine righteous people who do not need to repent.

8-9 ‘Or suppose a woman has ten silver coins and loses one. Doesn’t she light a lamp, sweep the house and search carefully until she finds it? And when she finds it, she calls her friends and neighbours together and says, “Rejoice with me; I have found my lost coin.”  10 In the same way, I tell you, there is rejoicing in the presence of the angels of God over one sinner who repents.’ Luke 15:1-10 New International Version

Can you imagine the exciting hope that these two parables Jesus told would have given to people who knew their lives were in a mess? The tax collectors and 'sinners' of those days (which would've included prostitutes and drunkards) were very aware of how religious people despised them. Yet here was this holy man of God who not only welcomed them at His meetings, but told stories that showed that their lives were valuable to God! Both parables spoke of the sheer joy of people who find something that was lost. But Jesus wasn't talking of just people, He refers to the rejoicing that takes place in heaven in the presence of the angels when even one sinful person repents of sin and turns away from the life they were living to trust in God. Jesus showed that every soul is precious, even those who have drifted the furthest from God.

But does vs 7 imply that some people are good enough to not need to repent?

The answer must surely be no, because the Bible teaches elsewhere that all people have gone astray and there are none who so righteous that they don't have to start with repentance. I suggest Jesus was simply pointing out that those who had already turned to God and were seeking to live righteous lives ought to rejoice as the angels do when someone who was living in sin hears the gospel and repents.

The whole incident shows us the dark side of religion when it focuses on one's own achievements instead of on God's grace. When religion consists of what we think we are doing for God rather than realizing how much God has done for us, it can make us hard hearted and judgemental. We see that attitude a lot in religion today. But both parables spoke of someone seeking what was lost, and rejoicing when they found it. Christians realize that they were lost in sin, but God sent Christ to seek and save that which was lost. They know that it was God's mercy that gave them righteousness and they will want to tell of that mercy to others, even to the greatest sinners in society.

There's perhaps another lesson here which comes out in the parable that follows where Jesus told of a son who begrudged his father's mercy to his wayward brother. Many Christians are people who, in God's grace, grew up in homes where they had Christian parents. They may have turned to Christ when they were young and not gone down sin's darkest paths. Their conversion experience is not as dramatic as when people whose lives were in a terrible mess get converted. But I’d say that they too should rejoice with the angels when people they wouldn’t have associated with are saved. In fact, it may be through having more social contact with such people that they are saved. Jesus ate with sinners and had conversations with them. And if such people are converted we should invite our Christian friends and neighbours to rejoice with us that there are some new members in God's family.