Leaving the Gospels briefly, let's focus today on an interesting textual variant in First John 4:3. The Byzantine text reads Ἰησουν χριστον ἐν σαρκἱ ἐληλυθοτα, and the Nestle-Aland/UBS compilation reads τον Ἰησουν. In favor of the non-Byzantine we have A B 322 323 945 1241 (which can be viewed here) and 22989 and, regarding versions, the Vulgate, the Coptic (Bohairic), and where patristic evidence is concerned, Clement Origen Socrates' MSS (as explained in the UBS apparatus), Cyril (4 out of 5 citations), Tertullian (1 out of 2 citations), Lucifer (the Sardician bishop, not the devil), Tyconius (2 out of 3), Ambrose, Augustine, and Fulgentius (1 out of 2).
As the late professor Bruce Manning Metzger observed, the shorter reading is supported by "good representatives of both Alexandrian and Western types of text." I agree with Metzger's assessment that later copyists expanded the verse by borrowing language from the previous verse. This is a benign expansion in the Byzantine text - but an expansion nonetheless.