This Epistle of Paul to the saints is said to the Wisdom epistle and is one of his prison epistles. It reminds the believer about his/her position in Christ and is considered to be written to the general body of Christ as it do not contain any personal greetings. The term "in Ephesus" is not found in the earliest manuscripts. This could be ascribed later by scribes becaue Ephesus was the leading region where Paul did his missionary activities for about 3 years (Acts 18:19-21, 19:1, 8-10, 20:31). Neverthless this is for the saint who are faithful (1:1). This is written about AD 61-63 towards the end of his 3rd missionary journey in Rome as prisoner (Acts 28:16, 30-31; Eph 1:1, 3:1, 6:20). This letter was delivered by Tychicus who carried this to the saints (Eph 6:21-22).
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