No good shepherd would leave 99 for 1 sheep. Why did Jesus give such a parable?

On the contrary, Jesus expects his disciples to know that anyone would leave 99 to search for 1. This fact is implied in the narration. In Matthew, Jesus asks, “Does he not leave the 99?” In Luke, he asks, “What man of you does not leave the 99?”

In Matthew, the parable follows a statement of mission: “For the son of man is come to save that which was lost.” Apparently, in Matthew, Jesus gave the parable to help his disciples understand why that mission would be undertaken.

In Luke, the parable follows a report that the Pharisees and the scribes murmured at the association of Jesus with sinners. Apparently, in Luke, Jesus gave the parable, along with two others (the lost coin and the prodigal son), as a dig at the Pharisees and scribes. Elsewhere he responded to their murmuring by citing the fact that not the whole, but the sick, need the physician.

Regardless of these apparent reasons that Jesus gave the parable, the parable is most important because it depicts accurately the state of his own affairs—Jesus had twelve apostles, and one of them was gone astray and lost. The parable tells us how he handled his own state of affairs. He left the eleven for the one.

The good news is that he lost none of the eleven in the process of raising up the one again.