Exegesis:

ho eis ton agron ‘the man (working) in the field.’

eis here equals en ‘in’ (cf. 1.9).

agros (cf. 5.14) ‘field,’ ‘plot of ground.’

mē epistrepsatō eis ta opisō ‘he is not to go back (to the house)’: the man working in the field is enjoined to flee at once without taking time to go back to the house and get his cloak.

epistrephō (cf. 4.12) ‘turn around,’ ‘turn back’: here, with eis ta opisō (literally, ‘to the places behind’), it means ‘go back,’ ‘return.’

himation (cf. 2.21) ‘outer garment,’ ‘cloak,’ ‘mantle.’

Translation:

Turn back is often rendered as ‘return to his home.’

Let him … not turn back may be translated as a statement of obligation, e.g. ‘a man who is in the field should not return to his home to get his cloak.’

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 .