Augustine of Hippo — as excerpted in the Catena Aurea on John 6:35-40

“(de Cor. et Gratia, c. ix) They therefore who by God’s unerring providence are foreknown, and predestined, called, justified, glorified, even before their new birth, or before they are born at all, are already the sons of God, and cannot possibly perish; these are they who truly come to Christ. By Him there is given also perseverance in good unto the end; which is given only to those who will not perish. Those who do not persevere will perish.”