Exegesis:

hotan aparthē ‘when he is taken away’: the subjunctive mode of the verb is required by the sentence construction; its meaning, however, is not ‘when he may be taken away,’ as though doubt were expressed, but, simply, ‘when he is taken away,’ a statement of future fact.

apairō (the word occurs only here and parallel passages Mt. 9.15, Lk. 5.35, in the N.T.) ‘take away,’ ‘remove’: the verb, as such, does not state whether the removal is natural, or sudden and violent. The context of the whole saying, however, implies a violent removal which will provoke sorrow (cf. the use of the verb in the Septuagint Isa. 53.8).

nēsteusousin ‘they will fast’: a declaration of what will happen in the future, not a command.

Translation:

In place of the days some languages employ ‘the day’ as an expression of indefinite temporal reference (Amganad Ifugao). One may, of course, also translate ‘the time will come.’

Is taken away may in some languages be paralleled by ‘is caused to go away’ or ‘is led away,’ since objects may ‘be taken’ but people are either ‘caused to go’ or ‘are led.’

Quoted with permission from Bratcher, Robert G. and Nida, Eugene A. A Handbook on the Gospel of Mark. (UBS Handbook Series). New York: UBS, 1961. For this and other handbooks for translators see here .