What does John 10:12 mean?
Jesus is making the third of three analogies which use the theme of shepherding. A main point of this third parallel is that Jesus is the "good shepherd," in contrast to those who have selfish interests at heart. Jesus comes to offer life (John 10:10). He does this with humility and self-sacrifice (John 10:11). Prior statements compared some religious leaders to thieves and robbers, who purposefully take advantage of the flock for their own gain (John 10:1, 8; Ezekiel 34).Here, Jesus refers to those who serve the flock, in a sense, but who are not motivated by love and self-sacrifice. A hired shepherd, for instance, is inclined to run away when the sheep are under severe threat. That hired hand is only interested in the sheep so long as he benefits; when serving the sheep means personal risk, he abandons them. This describes those who purposefully take advantage of others using spiritual deception. But it also applies to those who "passively" take advantage: claiming spiritual authority or privilege without the service or sacrifice that position entails.
This also connects to a famous statement made later in this chapter. Jesus will claim that the life He offers is eternal, secure, and absolute: "no one will snatch them out of my hand" (John 10:28). The root verb used in this verse is harpazō. Jesus' later statement uses this exact same root word, differing only in tense. As the one and only "good shepherd," Jesus will never allow any of His sheep to be taken from Him. Full stop.