Blessed Peacemaker wrote: Jesus says, "My sheep hear my voice and they follow me." That's not the same as "My sheep are chosen and all their sins are forgiven in advance."
"My sheep hear my voice" Who hears? - "My" sheep. Who hears "MY VOICE"? - "My" sheep.
Who becomes "MY" sheep? the disciples of Jesus? John 6:44 No man can come to me, except the Father which hath sent me draw him: and I will raise him up at the last day."
Those whom the Father has drawn. That is the elect - that is the chosen. God alone does the choosing, electing and the drawing to Jesus. Man can't because sin dominates him, sin blinds him. 1Cor 2:14.
Those who are not chosen/elect cannot hear the voice of Jesus nor can they respond.
Btw. Sinners only are chosen and elected by God. No advance purification is necessary. "This is a faithful saying, and worthy of all acceptation, that Christ Jesus came into the world to save sinners; 1Tim 1:15.