Jesus continued teaching with another agricultural parable. The "seed" sown is the word of God, of course (cf. Luke 8:11). Jesus' purpose here is to make a spiritual comparison between scattered seed and the kingdom of God (i.e., the church).
The first step is for the seed to be sown and then left to work its power. After seed is scattered, its sprouting does not depend upon the sower. Once the sower sows the seed, there is nothing he can do to force the seed to sprout. This is true physically and spiritually because man does not understand how the seed sprouts. Physically, even with all of today's technology, man does not comprehend how life sprouts from the seed. We only know that rain, sunshine, and suitable soil are necessary. Once the farmer plants the seed, all he can do is rest in the hope that it will sprout. Spiritually, we know that a good and honest heart is a requirement, but we will never understand or be able to predict why a certain person is receptive and others aren't to the same gospel message. Let it always be remembered that the sower's job is to sow and not to understand everything that happens afterward. We must faithfully sow the seed and then pray for it to sprout! Physically and spiritually speaking, the growth is with God (cf. I Cor. 3:6-9)!
In Mark 4:28, Jesus described the orderly development of the sprouted seed - "First the blade, then the head, after that the full grain in the head." This growth is in harmony with physical and spiritual laws. One should not expect to find the ripened Christian mindset and maturity in the young convert any more than one should expect fully developed corn one day after planting. All growth takes time. The sower must be patient and sensitive to the young plant and its needs.
Mark 4:29 states - "But when the grain ripens, immediately he puts in the sickle, because the harvest has come." Physically, this is not difficult to comprehend. When the harvest is ready, there is work to be done. Spiritually, since it appears that the sower is the one doing the reaping, this could be understood as the in-gathering of souls into the church or kingdom of God. After the seed is sown, it will sprout if it is heard and believed (cf. Rom. 10:17; Heb. 11:6). Faith will blossom into repentance (cf. II Cor. 7:10; Acts 17:30) and the great confession (cf. Rom. 10:9,10). Finally, the individual is born again and added to the kingdom via baptism for the remission of sins (cf. Acts 2:38,47; John 3:3-5; Gal. 3:27). Spiritually, one should sow the gospel seed into a person's heart and then continue watering it and nurturing it so that fruit can be harvested for the Lord. There is still, of course, a need to water the seed even after the individual becomes a part of the kingdom.