Charles Spurgeon Commentary John 10:3

"To him the porter openeth; and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out." — John 10:3 (ASV)

And the sheep hear his voice:

Those who are really chosen of God hear and heed the voice of Christ, but those who are not Christ's chosen ones will not heed his discourse, but will listen to the many voices which attract the ears and the hearts of sinful men. The elect of God are known by this mark, that they hear the voice of Christ. Just as you can find out, in a heap of ashes, whether there are any pieces of steel there by simply thrusting in a magnet, so can you find out God's chosen people by the mighty magnet of Christ's voice.

And he calleth his own sheep by name, and leadeth them out.

Sometimes he leads them out from the midst of the world's flocks, and sometimes he calls them by name when they are in his fold, and leads them out to even higher and better pastures, calls them and leads them out to higher truths than they have received before.

To him the porter openeth and the sheep hear his voice: and he calleth his own sheep by name, and leadeth them out.

John the Baptist was the porter who opened the door of Christ's earthly ministry by bearing witness that he was the Son of God.