John 6:64-66  But there are some of you that believe not. For Jesus knew from the beginning who they were that believed not, and who should betray him. And he said, Therefore said I unto you, that no man can come unto me, except it were given unto him of my Father. From that time many of his disciples went back, and walked no more with him.

   This must be an inward reality through faith((Christ in us)), or the devil owns it.  Notice the work of knowing Him and denying Him is verse 666, it is the finality of men rejecting GOD and thereby sealed as the reality of men being beasts as, opposed to in His image, and eternally dead.

   Take these verses to heart in the coming days as the darkness covering the earth takes hold for a short terrible time:  Hebrews 10:35-39    Cast not away therefore your confidence, which hath great recompence of reward. For ye have need of patience, that, after ye have done the will of God, ye might receive the promise. For yet a little while, and he that shall come will come, and will not tarry. Now the just shall live by faith: but if any man draw back, my soul shall have no pleasure in him. But we are not of them who draw back unto perdition; but of them that believe to the saving of the soul.