Stern Warning in John 9-10
Jesus said, “For judgment I have come into this world, so that the blind will see and those who see will become blind.”
Some Pharisees who were with him heard him say this and asked, “What? Are we blind too?”
Jesus said, “If you were blind, you would not be guilty of sin; but now that you claim you can see, your guilt remains. Very truly I tell you Pharisees, anyone who does not enter the sheep pen by the gate, but climbs in by some other way, is a thief and a robber. The one who enters by the gate is the shepherd of the sheep. The gatekeeper opens the gate for him, and the sheep listen to his voice. He calls his own sheep by name and leads them out."
John 9:39 through John 10:3

Jesus gave a stern warning in John 9 and 10 to the Pharisees after they had kicked out of the congregation the man whom Jesus had healed of blindness on the Sabbath. Jesus made the point that entering the sheep pen is legitimate only when that legitimacy comes from Jesus Himself. No man has the right to give that legitimacy, and if anyone tries to be the one who legitimizes others, he is a thief and a robber.
The Pharisees kicked out the healed man because he dared to claim he knew Jesus was from God, and they had already proclaimed they alone could legitimize Jesus. Let us tremble in fear that we never take the position that we have the right to legitimize another! Only Jesus can do that!