Exegesis:
ho christos (cf. 8.29) ‘the Messiah,’ ‘the Christ.’
ho basileus Israēl (only here in Mark) ‘the King of Israel.’
katabatō (cf. v. 30) ‘he must descend,’ ‘let him come down.’
hina here indicates purpose, ‘in order that,’ ‘so that.’
idōmen kai pisteusōmen ‘we may see (it) and believe (that he is the Messiah).’
pisteuō (cf. 1.15) ‘have faith,’ ‘believe.’
hoi sunestaurōmenoi (only here in Mark) ‘those who had been crucified with.’
ōneidizon (16.40) ‘they were reviling,’ ‘they were insulting.’
Translation:
Let the Christ … is a kind of third person command, not an expression of permission, as some translators have taken it. However, a third person imperative is rather rare in languages and hence some paraphrastic equivalent must be employed. These are generally of two types: (1) a shift to second person, e.g. ‘you claim to be the Christ, the King of Israel, come down … so that we may…’ and (2) a statement of obligation, e.g. ‘the Christ, who is the King of Israel, should come down … so that we may….’ In general the latter method is preferred, for it eliminates the necessity of relating ‘you’ to ‘the Christ’ by some phrase which would be out of keeping with the attitudes of the chief priests and scribes. ‘You who are the Christ’ would be entirely out of harmony with the context.
Christ, the King of Israel, which is an appositive phrase, must be made a relative clause in some languages, e.g. ‘Christ who is the King of Israel,’ and a paratactically combined explanation in others, e.g. ‘Christ, he is the King of Israel.’
For the King of Israel see comments under the King of the Jews (15.2).
See is often a transitive verb in various receptor languages, thus requiring an object, e.g. ‘see you (or ‘him’) do it.’ Likewise believe may be translatable only as a transitive, e.g. ‘believe in you’ (or ‘him’).
Reviled him may be rendered as ‘heaped insults on him,’ ‘denounced him,’ or ‘said bad things about him.’
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 .