Ninety-nine stay, and he goes after one.
It is only four verses, and they hold a decision no sensible manager would make: leave ninety-nine sheep in the wilderness to look for one.
Luke tells us why Jesus told it. The Pharisees and the scribes were murmuring: "This man welcomes sinners, and eats with them." The lost sheep is the first answer.
I tell you that even so there will be more joy in heaven over one sinner who repents, than over ninety-nine righteous people who need no repentance.
The sentence is spoken to people who counted themselves among the ninety-nine. Heaven, he says, rejoices more over the one sheep found than over the safety of the rest. Anyone complaining that Jesus ate with sinners was, in effect, complaining about the party.
The parable never shows the sheep repenting. It gets lost, is searched for, is found and is carried. All the action belongs to the shepherd. When Jesus speaks at the end of "one sinner who repents", the picture he has just given for it is being found.
And the sums are wrong on purpose. Risking ninety-nine for one is not good flock management. It is a portrait of someone for whom each one has a name — which, to his listeners, meant that the "sinners" he ate with were not an acceptable percentage of loss.
Walking with Jesus has a collection called The Parables of Jesus that takes them one a day — each with the question he was answering, a short reflection, a prayer, and one thing to carry into the day.
It is a one-time purchase, about five minutes a morning, and it never asks you to catch up on days you missed.