en_tn/mrk/04/29.md

he immediately sends in the sickle

Here "the sickle" is a metonym that stands for the farmer or the people whom the farmer sends out to harvest the grain. Alternate translation: "he immediately goes into the field with a sickle to harvest the grain" or "he immediately sends people with sickles into the field to harvest the grain" (See: rc://en/ta/man/translate/figs-metonymy)

sickle

a curved blade or a sharp hook used to cut grain

because the harvest has come

Here the phrase "has come" is an idiom for the grain being ripe for harvest. Alternate translation: "because the grain is ready to be harvested" (See: rc://en/ta/man/translate/figs-idiom)