Not every textual variant of the Greek New Testament shows up in the MSS of the NT. The case I have in mind is Origen’s citations of Mark 10:18 and Luke 18:19 (cf. also Mark 2:7 and Matthew 19:16). In his Commentary on Matthew (15,10; loc. in comm. not the Gospel of Matthew), written late in Origen’s life, he notes that Mark and Luke quotes the Savior as saying τι με λεγεις αγαθον; ουδεις αγαθος ει μη εις ο θεος (“Why do you call me good? None is good except one: God”). This is one of those places where Origen has to be clear about what his text reads as he is saying that both Gospels read the same. Based on our critical text today, he is correct.
However, Origen had earlier cited this text six times in his extant writings, but in each of these occurrences he added ο πατηρ after ο θεος, so the text now reads, “…no one is good except one God the Father.” Thus, the citation in the Matthew commentary is singular among Origen’s references to this text. This addition of “the Father” occurs in four different works. His first and second books of his commentary on John, written while he still lived in Alexandria (before 231), contains the citation twice (Commentary on John 1,254, 2,96). This reading is retained in the sixth book of his commentary on John (6,245) completed after his move to Caesarea (c. 231-3). The longer citation also occurs in Origen’s apology of the Christian faith against Celsus (Contra Celsum 5,11). Finally, the longer text occurs in two of Origen’s hortatory works, Exhortation to Martyrdom (7; ca. 235) and On Prayer (7; ca. 233-4).
Kirsopp Lake and company (“The Caesarean text of the Gospel of Mark,” Harvard Theological Review 21:4 , 207-404), argued that the addition of ο πατηρ was a “characteristic Alexandrian variant” based apparently on the fact that Clement of Alexandria had used it, though no NT MSS support exists for the longer reading. (I got this last point from Fiona Thompson’s “The Text of the Synoptic Gospels in the Writings of Origen” (Ph.D. diss; University of Leeds, 2005), 415.
Origen’s use of an alternate text not found in the Greek MSS of the NT raises the interesting question about what to do with his reading in terms of the transmission of the NT. Just because this reading does not match any known NT MSS does not make it any less a textual variant.
Personally, I think it, and other variants of this nature, should be included in future textual apparatuses of the NT that include the Church Fathers. The evidence here from Origen points in the direction that the longer form of the text is how he knew it in Alexandria. One wonders if his exposure to other MSS as he built his library in Caesarea caused Origen to change his view on the text by the time he wrote his Commentary on Matthew.