Sheep depend upon shepherds for their welfare. In John 10:1-21, Jesus continues a conversation He's been having with some Pharisees. He speaks of sheep knowing their shepherd's voice. He also described how thieves and robbers get into sheepfolds to wreak havoc among the sheep. The Pharisees in Jesus' day were those whom Jesus classified as thieves and robbers. They didn't care for God's sheep. Jesus DID care. In fact, He would lay down His life for the sheep.
