Parable of the Growing Seed

"He was saying, 'The kingdom of God is like a man who casts seed upon the soil; and goes to bed at night and gets up by day, and the seed sprouts up and grows-how, he himself does not know. The soil produces crops by itself; first the blade, then the head, then the mature grain in the head. But when the crop permits, he immediately puts in the sickle, because the harvest has come.' "

Mark 4:20