Jesus was proclaiming the kingdom of God was at hand—himself—and his people were not receiving him in that role, but as a healer or political threat. Seeing this, he chose to speak in parables, for those who were receptive would catch their thinly-veiled meanings.
The parable of the soil (Mark 4:1-20) as it should be called, has been debated in terms of who’s saved and who’s not. I’d say that the truly saved upon reading this parable will immediately sense there’s more to the story than a stepping off point to a debate. Here the first commentary consulted should be the Lord’s explanation that follows it. What else is needed?
Note in all cases the sower and seed are the same, but the soil varies. One question quickly pops into my head. Can I cultivate myself so that the seed sown—the Word if God—will grow? I’d say absolutely, by removing the cares and concerns of world and all of its allurements, by a keen sensitivity to and examination of what the Word says and means, by seeking through prayer the Holy Spirit’s illumination and guidance into all truth, and so forth. Once said this way, to be fruitful, you had better be capable of a lot of self-discipline and in possession of a resolute heart, or simply saved!
The telltale sign of a saved person is a voracious hunger for the Word of God. The Holy Spirit does the clearing, plowing, and irrigation.
Truth is, nothing grows in an unregenerate heart.