There is a very important lesson to be learned through the Parable of the Soils. When Jesus said, "Do you not understand this parable? How then will you understand all the parables?" He was admonishing the reader of this parables great importance. Although Jesus explains the parable, Mark 4:15 should cause believers to become keenly aware that a battle rages in the spirit to try and stop faith from growing in believers. This is a very important key, because everything that believers receive from God comes the same way, through faith.
Notice the first thing that happens when the Word is sown, "Satan comes IMMEDIATELY to take away the WORD that was sown." It does not matter if you are sitting in a pew, watching a preacher on television, reading the Bible or listening to the word on radio, Jesus tells us that Satan will come and do one of the things that he does best, STEAL."The thief does not come except to steal, and to kill, and to destroy..."
Take note to where the word was sown, IN THEIR HEARTS. This is a very personal invasion and believers should NOT permit Satan access to their hearts. I say it this way because that is exactly what believers do.
I John 3:8 says, "He who sins is of the devil, for the devil has sinned from the beginning. For this purpose the Son of God was manifested, that He might destroy the works of the devil." Jesus has destroyed the works of the devil! Satan has no authority over the believer unless the believer CHOOSES to give him place. So yes, it become the choice of the believer to permit Satan access to their heart.
The heart is the seat of spiritual life, moral nature, and affections, so an attack such as this should be seem as horrible a rape. Also take notice that the scripture says, “In their HEARTS” (plural). Satan’s interest is not in a couple of people, but as many as he can steal the word from. His assault is to the very core of ones faith. Take the word from ones heart, faith will never grow and if faith doesn't grow believers will never come to know the privileges and receive the promises of God through Christ.
"So then faith comes by hearing, and hearing by the word of God." (Romans 10:17)