Exegesis:

anastenaxas tō pneumati autou ‘sighing deeply in his spirit,’ ‘groaning inwardly.’

anastenazō (only here in the N.T.; cf. stenazō 7.34) ‘sigh deeply,’ ‘groan.’

tō pneumati autou (cf. 2.8) ‘in his spirit,’ ‘in himself.’

ti ‘why?’: so most translations and commentators. Black takes it to mean ‘how?’

genea (8.38; 9.19; 13.30) ‘race,’ ‘kind,’ ‘generation’: here used of the contemporaries of Jesus.

ei dothēsetai … sēmeion ‘if a sign shall be given’: a Hebraism indicating strong denial, ‘no sign shall be given.’ As Arndt & Gingrich point out, an unexpressed wish, or oath, is implied: ‘may this or that happen to me if….’ Only here and in the quotation from Ps. 95.11 in Heb. 3.11, 4.3, 5 does this idiom appear in the N.T.

Translation:

Spirit must not be translated in such a way as to imply (1) the Holy Spirit, (2) the spirit which lives on after death, or (3) a familiar spirit, or demon. (This last meaning has been unfortunately entirely too frequent in translations.) In many languages one can use ‘heart,’ ‘liver,’ ‘stomach,’ or some other emotional center of the personality.

Sighed in his spirit in San Mateo del Mar Huave is ‘to let out the air from his heart.’ In Copainalá Zoque the opposite action forms the basis of the figure, ‘he drew a breath in his heart.’

This generation is ‘the people now’ (Chol) or ‘those who are in space now’ (Tzeltal). In some instances it must be made clear that the Pharisees who posed the question are included in this group, e.g. ‘you people now living.’

Truly is often translated with one of two different syntactic relations (1) ‘I tell you the truth; no sign shall be…’ or (2) ‘I tell you, Certainly no sign shall be….’ That is to say, the adverb is related to the verb of speaking, as an assertion of the truth of the utterance, or combined with the object of the verb of speaking, namely as a statement about the certainty of the event described. The ultimate results are practically the same, though the receptor languages in question may require one or the other syntactic relationship.

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 .