As Jesus was teaching and preaching throughout the Galilee, he was constantly getting into trouble with the religious leaders of his day. His habit of welcoming and pursuing societal outcasts and sinners was frowned upon. But in Jesus' mind, this is what the kingdom of God was all about - God pursuing broken and lost people, no matter the cost.
In Luke 15, Jesus is confronted again by the religious leaders because of his table fellowship with tax collectors and sinners. Jesus' response is a teaching - a parable. It's a famous parable from the mouth of Jesus, but it's also a subversive and challenging parable. Do we understand the costly nature of God's pursuing love? How will we respond? How will we treat our neighbors and enemies in light of this costly love?