God will not allow Christ's sheep to be snatched out of His hand NOT because of the man made idea of eternal security, that some add to the text, but because the sheep are faithful in their hearing and following Christ, v27. If the sheep become unfaithful in their hearing and following, they remove themselves from God's hand.
what sort of shepherd folds his hands and says, 'my sheep will be fine; they always come when i call them'
and does nothing to drive away the wolves?
Suppose one of you has a hundred sheep and loses one of them.
Doesn't he leave the ninety-nine in the open country and go after the lost sheep until he finds it?
(Luke 15:4)
the Shepherd i know pulls me out of the brambles when i'm entangled, and drives away jackals and robbers when they seek to capture me.