[5:21] 1 tc Most later mss (P Ï) have ἀμήν (amhn, “amen”) at the end of this letter. Such a conclusion is routinely added by scribes to NT books because a few of these books originally had such an ending (cf. Rom 16:27; Gal 6:18; Jude 25). A majority of Greek witnesses have the concluding ἀμήν in every NT book except Acts, James, and 3 John (and even in these books, ἀμήν is found in some witnesses). It is thus a predictable variant. Further, the earliest and best witnesses, along with several others (א A B Ψ 33 323 630 1505 1739 al sy co), lack the inoffensive particle, rendering its omission as the authentic reading.
