Exegesis:
hotan de paradoi ho karpos ‘when the fruit allows,’ i.e. ‘when the crop permits’: so, in a general sense, “when the grain is ripe” (Revised Standard Version).
paradidōmi here has the sense of ‘permit,’ ‘allow’ (this is the sense of the Greek text, but thinks that the underlying spoken Aramaic probably meant ‘when the fruit has been produced’). For the use of paradidōmi ‘hand over’ see 1.14, 3.19.
apostellei to drepanon, hoti parestēken ho therismos ‘he sends forth the sickle, because the harvest has come’: the words reflect an O.T. passage, Joel 3.13 (LXX, 4.13).
apostellō ‘send’: Field argues for the meaning ‘put forth’ on the basis of the Hebrew verb shalach ‘send forth,’ ‘stretch out’ which in Joel 3.13 the Septuagint translates exapostellō ‘send forth.’
to drepanon (only here in Mark) ‘sickle’: by a change of figure ‘sends forth the sickle’ stands for ‘sends out the reapers’ (Gould; cf. The Modern Speech New Testament).
hoti here is causative ‘because.’
paristēmi (14.47, 69, 70; 15.35, 39) ‘is present,’ ‘stands by’; ‘is ready.’
ho therismos (only here in Mark) ‘harvest,’ ‘time of harvest,’ ‘harvesting.’
Translation:
Ripe is rendered variously as ‘hard,’ ‘complete,’ ‘ready,’ and ‘fully grown.’
Puts in the sickle may refer to either (1) the immediate process of cutting the grain (by the grammatical subject of the expression), e.g. ‘he cuts it down’ (Copainalá Zoque, Southern Subanen) or ‘cuts with a rounded machete’ in which ‘rounded machete’ is the name of the harvesting sickle (Tabasco Chontal), or (2) the sending of workmen into the harvest fields to do the work (seemingly the preferable rendering), e.g. ‘sends those who bear the knives,’ in which ‘knives’ is the cultural equivalent of sickle (Shipibo-Conibo); ‘gives the order to those who cut with the sickle’ (Batak Toba).
Harvest is ‘the time of cutting’ (Barrow Eskimo) or ‘harvesting-time’ (Shipibo-Conibo).
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 .