Matthew 18:12

“Does he not leave the ninety and nine, and go to the mountains, and seek that which is going astray?”

And what does the Shepherd do when He finds that one has gone astray? Why, He goes out into the mountains to seek the one who has gone astray. Note the emphasis on the cost. He ‘goes to the mountains' to seek the one which is lost. A real effort is put in and a real price is paid. In one sense the Shepherd here is the Father. It is His concern that is being described (Matthew 18:10; Matthew 18:14). But He does it, of course, through His shepherds; through Jesus, and through all who follow Jesus truly.

He ‘leaves the ninety nine' in the care of others. To the average person of that day ‘ninety nine' would be a discordant number. The fullness suggested by one hundred has been broken. The divine shepherd cannot therefore rest until fullness is restored for every member of the flock is of equal importance.

(In actual fact it is doubtful how many, if any, of the shepherds, could count to a hundred. They would know that the sheep was missing because they knew them all by name (John 10:3). They would not even know how many they had left behind. But they would know that it was an incomplete number. It was ‘ninety nine' not ‘a hundred').