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Jesus comforts the church in Philadelphia with this message: to know who He is and that He knows them, that He gives them purpose and His Word, and that Jesus is with them now and forever.
Paul encourages and exhorts Timothy to stay in the Word. He tells him he has everything he needs in the scriptures because God has spoken His Word through them.
The parable of the soils is not about which soils are the Christians, but is about the dynamic nature of hearing the Word. What matters is hearing the Word in a way that bears fruit.
Growing in faith works the same today as it did in Jesus' time. A seeking person hears the Word of God and believes and takes a step of faith. God confirms His Word and the seeker's faith grows bigger.