Jesus told them
εἶπεν δὲ πρὸς αὐτοὺς τὴν παραβολὴν ταύτην λέγων
Luke indicated that Jesus wanted to justify his behavior. Thus, he told them (εἶπεν δὲ πρὸς αὐτοὺς) this parable (τὴν παραβολὴν ταύτην λέγων). This parable of the lost sheep can also be found in Matthew, chapter 18:12, with some minor changes. Perhaps this is a Q source. Matthew indicated that Jesus asked them to think (Τί ὑμῖν δοκεῖ) about these things or this parable, although he did not call it a parable like Luke did here. Do you like stories or parables?