After delivering the Parable of the Sower, Jesus revealed privately to his disciples that the seed is the word of God (Luke 8:11), which is sown in a man’s heart (Luke 8:12, 15). The hearts of some men are described in Luke 8:5-8 in varying degrees of receptiveness to the word of God, which is what makes the hearts of men useful to the Kingdom of God. In Luke’s first example, he tells us that some men’s hearts are just too hard for spiritual life (Luke 8:5, 12). The hearts of these men are trodden down, as though their hearts had no value (Matthew 7:6; cf. Hebrews 10:29) The birds eat the seed deposited there, so the word of God is never permitted to take root so that these men might consider the will of God.
The second example of a man’s heart shows some receptivity of God’s word, but the soil is too shallow upon a bed of rock (Luke 8:6). Having no moisture, the plant produced by the seed withers and dies. In the third example Luke tells us that the ground (a man’s heart) is fertile enough, but the seed is sown among thorn seeds (Luke 8:7), which grow faster than the good seed. The life of the thorn seeds compete with and overpower the life of the good seed, thereby causing the good seed (the word of God) to be unfruitful. In other words, such a heart is always immature in the ways of God.
In Luke 8:8 Jesus tells us that the honest (G2570) and good (G18) heart is ready for the word of God. This heart is a better (G2570) and a beneficial (G18) heart, one that would be very fruitful with respect to the Kingdom of God. So, it becomes clear that the Parable of the Sower is all about the condition of men’s hearts, and the heart’s value in the Kingdom of God. The Parable of the Sower has nothing to do with salvation, as some might think. Rather, it is all about fruitfulness. Using this parable to determine who is and who is not a disciple of Christ, leads only to judging others, something Jesus told us not to do (cf. Luke 6:37).
According to Luke 8:12, the birds (Luke 8:5) are the devil, which probably does not mean the spirit being (Satan) so many think of, when the word devil is mentioned. Rather the term devil (diabolos – G1228), according to Paul, refers to slanderers and false accusers (1Timothy 3:11; 2Timothy 3:3; Titus 2:3). This rendering of the word fits perfectly into the context of Jesus’ life at this point. Jesus’ own slanderers and false accusers were the Pharisees and rabbis (Matthew 12:24; Mark 3:22). If we take such a matter into consideration, the devil (diabolos – G1228) of Luke 8:12, symbolized by the birds in Luke 8:5 would point to the Pharisees and rabbis who had given Jesus so much trouble during his ministry (cf. Luke 11:52).
The Pharisees and rabbis were able to take away the seed, meaning the word of God (Luke 8:5, 12), by challenging those who were obedient to Jesus (Luke 5:30; 6:2), and belittling their response to Jesus’ words (cf. John 7:45-49) and pretending they knew better than those who might challenge them (cf. John 7:50-52). The problem of the heart in Luke 8:6, 13 is that it has no depth. The heart is still hard and lacks moisture to strengthen the life of the seed. Moisture in this context refers to the Holy Spirit, whom Jesus points to in John 4:10, 14 and John 7:37-38. The Holy Spirit softens the heart and adds nutrients to the word of God deposited there.
The problem is that man is unable to correct his condition. God must give him a new heart (Ezekiel 11:19; 36:26-27). It is simply illogical to believe we are able to soften our own hearts. Rather, a change of heart is required, and that can only be done by God. Once a man’s heart is changed, he needs to be careful what he allows his heart to consider. The heart in Luke 8:7, 14 is fertile enough to permit growth for the word of God, but problems arise when the work of God must compete with the desires of the flesh, which are the cares of the world and the pleasures of life etc. Multiple interests leave the word of God unfruitful in such a person’s life (cf. Luke 16:13). However, this condition can be reversed, if the thorns (cares and pleasures of life) are removed.
When one simply trusts God, all things will be added that are necessary for life (cf. Matthew 6:31-33). The difference in the heart Jesus mentions in Luke 8:8, 15 is that it has been prepared to receive the word of God. The ground has moisture, it is soft, and it has been worked, so that the thorns etc. have been removed. It is ready for the work of God, which means it will be fruitful for the sake of the Kingdom.