"You don't believe me because you are not my sheep." That hits pretty hard. Those who know Jesus' voice, who are "his sheep," believe him. It seems pretty simple, but it's a bit more complicated when we work it out in the day-to-day. It's hard to stay a sheep. Believing Jesus for what he says he will do, even in the face of great difficulty, often requires faith that we may sometimes doubt we're capable of.