"“Truly, truly, I say to you, he who does not enter the sheepfold by the door but climbs in by another way, that man is a thief and a robber. 2 But he who enters by the door is the shepherd of the sheep. 3 To him the gatekeeper opens. The sheep hear his voice, and he calls his own sheep by name and leads them out. 4 When he has brought out all his own, he goes before them, and the sheep follow him, for they know his voice. 5 A stranger they will not follow, but they will flee from him, for they do not know the voice of strangers.” 6 This figure of speech Jesus used with them, but they did not understand what he was saying to them."
John 10:1-6
The picture Jesus gives here is one that was familiar to His hearers, and this adds to the graphic way in which He exposes the false leaders of His day. Every true shepherd would as a matter of course make use of the door of the fold, and not climb over the wall or fence. The 'shepherd of the sheep' in 2 does not refer to Himself in this instance - He is the Door, not the Shepherd, in this part of the parable - but to any true and faithful leader, and the meaning is that the test of a true shepherd is his relationship to the Door, that is, to Christ. His work is related to Christ, and for His glory. It is centred on Him, and done in His strength. By this standard, the scribes and Pharisees stood condemned, for they repudiated Christ's authority altogether, thereby exposing the falseness of their own position and claim. This is an important lesson for us too: you can tell a true shepherd of God's people by his attitude to Jesus. If it is Christ-exalting, he is a true shepherd, if it is not, he is not. For the same kind of reason the sheep have an instinct for the right, and know whether the shepherd is true or not. There is something very important here: although, paradoxically, the sheep are silly creatures, they have an instinctive discernment, and when something is put before them they can sense, 'This is good and right' or 'There is something wrong here'. This is not a question of being theologically educated or literate, but of having a spirit of discernment, and this is why plain, simple, humble believers can often 'smell a rat' in teaching that can be plausible and very persuasive.