Mk 4:26-34
To ancient people, the scattering, the sprouting, the growing, and the resulting fruit were mysterious, as they did not have the biological knowledge which is available today. A biological understanding of germination and fruition does not necessarily remove the mystery or negate the parable.
The parable is about the kingdom of God, which grows without human intervention. The fruition of the kingdom is not dependent on people, for it is all God’s doing through Jesus, the proclaimer of the kingdom. The kingdom will continue its silent and slow growth until the day of the harvest, the apocalyptic end of the world.
The point that Mark is attempting to make by relating this parable is this: faith should yield more faith. In other words, the faith of one person should keep growing; there is never a time to stop. As faith continues to grow, so does the kingdom of God.
Just as the seed draws its life and nourishment from the soil, so the individual believer must draw his or her life and nourishment from prayer, the Scriptures, the sacraments, etc. These cannot become routine; otherwise, the growing stops. Growing in faith is a life-long endeavor; it is only at the moment of death that the individual grain is ripe and ready for the harvester. Throughout the growth, however, a person is unknowingly spreading the kingdom of God.