Charles Ellicott Commentary Mark 4:29

"But when the fruit is ripe, straightway he putteth forth the sickle, because the harvest is come." — Mark 4:29 (ASV)

He puts in the sickle.—From one point of view, here again, the harvest is the end of the world (Matthew 13:39), and the putting in the sickle is the coming of Christ to judge. (Compare the use of the same image in Revelation 14:14-18.) From the other, the harvest is the end of each man’s life, and the sickle is in the hands of the Angel of Death.