John Chrysostom

(Hom. xx. 1) Observe, He did not call them, before some had of their own accord joined Him: for had He invited them, before any had joined Him, perhaps they would have started back: but now having determined to follow of their own free choice, they remain firm ever after. He calls Philip, however, because he would be known to him, from living in Galilee. But what made Philip follow Christ? Andrew heard from John the Baptist, and Peter from Andrew; he had heard from no one; and yet on Christ saying, Follow Me, was persuaded instantly. It is not improbable that Philip may have heard John: and yet it may have been the mere voice of Christ which produced this effect.