What the Bible says about Seed as the Truth
(From Forerunner Commentary)
Jesus clearly says that the seed is "the word of the kingdom" (verse 19). It is what He plants in us to draw us out of this world and gives us an opportunity for salvation. It is the truth, the knowledge of God, the gospel, the whole counsel of God. It is described by many different terms.
Richard T. Ritenbaugh
Parables of Matthew 13 (Part 1): The Mustard Seed