jesus said, "I tell you the truth, the man who does not enter the sheep pen by the gate, but climbs in by some other way, is a thief and a robber. and The one who enters through the gate is the shepherd of the sheep. then the gatekeeper opens the gate for him, and the sheep recognize his voice and come to him. He calls his own sheep by name and leads them out. After he has gathered his own flock, he walks ahead of them, and they follow him because they know his voice. They won't follow a stranger; they will run from him because they don't know his voice."
Jesus used this illustration with them, but they didn't understand what he was saying to them.
But again jesus said to them, “Timeless truth I speak to you; I AM THE LIVING GOD, The Gate of the flock.” All who came before me are thieves and bandits, but the sheep didn't listen to them: and “I AM THE LIVING GOD, The Gate; if anyone will enter by me, he shall live and shall go in and out and shall find the pasture.” “But a thief does not come except to steal, kill and destroy; I have come that they may have life and have whatever is abundant.”
source from bible, John 10:1-10