where did the doctrine of once saved always saved come from
Perseverance of the saints The traditional Calvinist doctrine of perseverance is articulated in the Canons of Dort (chapter 5), the Westminster Confession of Faith (Chapter XVII), the 1689 Baptist Confession of Faith (Chapter 17), and may also be found in other Reformed Confessions. Nonetheless, the doctrine is most often mentioned in connection with other salvific schemes and is not a major focus of Reformed systematic theology (for instance, it does not even get a subheading in the three volume Systematic Theology by Hodge). It is, however, seen by many as the necessary consequence of Calvinism and of trusting in the promises of God.
Epistle to the Hebrews Scholars of Greek consider its writing to be more polished and eloquent than any other book of the New Testament. The book has earned the reputation of being a masterpiece.[6] It has also been described as an intricate New Testament book.[7] Scholars believe it was written for Jewish Christians who lived in Jerusalem.[6] Its purpose was to exhort Christians to persevere in the face of persecution. At this time, certain believers were considering turning back to Judaism (the Jewish system of law) to escape being persecuted for accepting Christ as their saviour, now following this system of grace (saved by Jesus' sacrifice on the cross). The theme of the epistle is the doctrine of the person of Christ and his role as mediator between God and humanity.