A slightly more complex apologetic rationale for scribal excision also may have existed: in parts of the early church represented by the tradition expressed in Apostolic Constitutions, regular fasts were to be observed on Wednesdays and Fridays, and fasting was to be avoided on Mondays, Thursdays, and Sundays. The fasts on Wednesdays and Fridays were said to commemorate Christ’s betrayal and His sufferings. But this may have provoked a question: what regular fasts did Jesus observe, before His betrayal and sufferings? Without the words και νηστεια in Mark , there is no evidence in Mark that Jesus regularly fasted during His ministry. The question would thus be rendered superfluous.
A copyist driven by a similar apologetic motive could remove the words in order to lower the risk that an unbelieving critic might pose a question such as the following: Jesus affirmed in Matthew 11:19 that he came eating and drinking. How, therefore, did he cast out a demon which can only be exorcised with prayer and fasting?
A much simpler explanation is also at hand: και νηστεια could be lost via a parableptic error elicited by homoeoteleuton. That is, an early copyist who was not familiar with the text accidentally skipped from the και in Mark 9:29 before νηστεια to the και at the beginning of Mark 9:30, thus carelessly losing the two words in between. The possibility of this kind of mistake might not naturally occur to readers of printed texts in which Mark 9:30 begins with κακειθεν, but when reading Codex W (from Egypt), in which Mark 9:30 begins with the non-contracted και εκειθεν, the possibility must be acknowledged.
The very same kind of careless mistake has caused the loss of και ανεσθη at the end of Mark 9:27 in Codex W, in Old Latin k (which, besides being the only Latin witness for the non-inclusion of και νηστεια in 9:29, is probably the most unreliable extant manuscript of the Gospel of Mark in any language), and in the Peshitta; according to the NA-27 apparatus this is also the likely reading of P45, which suggests that at this point Codex W and P45 echo an ancestor.
In a contest between the early church’s Christology, and the early church’s customs regarding fasting, the former had a much heavier impact on scribal habits. Copyists were far more likely to remove a short phrase which (they reasoned) risked giving the impression that Jesus was unable to exorcise certain demons without fasting previously, than they were to insert a short phrase which would risk giving readers exactly that impression.
If και νηστεια was not accidentally lost (or, if it was, and subsequent copyists in Egypt faced exemplars with rival readings in Mark 9:29), the perceived scandal at the thought that the King of angels needed to fast in order to exorcise a certain kind of demon, was enough to convince an early copyist in Egypt that the responsible thing to do was to protect readers from misinterpreting the text by removing the problematic words (or, if the words had already been accidentally lost, and a copyist faced rival readings in his exemplars, this line of reasoning would be a major basis for the adoption of the shorter reading).
I would also draw attention to the reading of Codex B in the subsequent verse, . Instead of παρεπορευοντο, B* reads επορευοντο. (So does D.) B*’s reading was adopted by Hort and Tregelles, but their judgment has been rejected by subsequent textual critics. Figuring that παρεπορευοντο is indeed the original text in , the reading in Codex B may be considered evidence that the text of B in this passage has undergone editing, which may have included theologically motivated editing.