Mark 4:27-31

and he goes to bed at night and gets up daily, and the seed sprouts and grows—how, he himself does not know.

The soil produces crops by itself; first the stalk, then the head, then the mature grain in the head.

Now when the crop permits, he immediately puts in the sickle, because the harvest has come.” Parable of the Mustard Seed

And He was saying, “How shall we picture the kingdom of God, or by what parable shall we present it?

It is like a mustard seed, which, when sown upon the soil, though it is the smallest of all the seeds that are upon the soil,