Exegesis:

tines tōn ekei hestēkotōn ‘some of those who were standing there,’ i.e. “some bystanders” (cf. 9.1 and 15.35).

ti poieite luontes ton pōlon ‘what are you doing untying the colt?’: the burden of the question, of course, is ‘Why are you untying the colt?,’ ‘What do you mean by untying the colt?’ (cf. Moffatt, Manson, Gould).

Translation:

Said to must often be translated as ‘asked’ because of the following question.

The periphrastic construction. … doing, untying … must be changed to ‘why are you untying…’ in many languages.

In some instances untying must be translated by a somewhat expanded expression, e.g. ‘untying the rope which is around the neck of the colt’ or ‘loosing the rope which is holding the colt.’

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 .