When Jesus sent His apostles out to preach the first time, He told them to go to a specific audience. He commanded them not to go to the Gentiles or the Samaritans, but go to the lost sheep of the house of Israel (Matthew 10:5, 6).
Luke 15 begins with the worst sinners in Jewish society gathering to hear Jesus preach. This riled the religious folk, so He told them a parable (Luke 15:3). A parable is a story based from nature or ordinary life that makes one grand, but often hidden, point. Some people will find the parable just a quaint story, others will perceive the hidden meaning.
A man (not a shepherd) with 100 sheep, finds that one has become lost. He leaves the 99 to find the lost one. When the lost sheep is found, the man carries it home on his shoulders and calls his friends to rejoice with him, For I have found my sheep which was lost (Lk 15:6).
While the religious leaders were complaining (Lk 15:2), Jesus said there was joy in heaven (Lk 15:7) over the repentant sinner.
In Christ’s parable, it’s not the lost sheep which seeks the man, but the man who seeks and finds the lost sheep to the man’s delight.
The Son of Man has come to seek and to save that which was lost (Luke 19:10).