The sermon discusses the parable of the two lost sons from Luke 15:11-32. In the parable, a father has two sons - one wastes his inheritance and ends up poor, while the other stays and works for the father. The poor son returns home seeking forgiveness and his father welcomes him back with a celebration. The message is about God's love and forgiveness for sinners, and his joy when they repent and return to him, just as the father rejoiced over his lost son's return.