In business, a cost/benefit analysis involves weighing the overall costs of a commercial activity to achieve the highest profit. With all of the cost involved in retrieving his one lost sheep, shouldn't the shepherd in Jesus' parable have just cut his losses and moved on with the other ninety-nine?
Apparently cost/benefit analysis wasn't used in tending sheep. In those days every single sheep was precious to the shepherd. A good shepherd would leave the other 99 to make a desperate search for one missing sheep. And in rescuing that one pathetic sheep, the shepherd would joyfully sling it over his shoulders to carry it home, gathering family and friends to celebrate when he got there.
In this parable of the lost sheep, the Reformers rediscovered a deep spiritual truth: God doesn't cut his losses on those who have gone astray. No, he goes after the lost when they are wandering in their sins, heading straight down the path toward destruction.
Just like lost sheep who can't find their way home, neither can sinners. God comes looking for us because we are helpless and hopeless, and because he is full of grace and mercy.
How should we respond to such amazing love? By giving ourselves completely to the one who has rescued us from sin and death.