In Matthew 13:10-17 Christ explains why he speaks to the people in parables. The reason he speaks in parables is both to reveal and conceal truth about the kingdom of God. This shows that the knowledge of the kingdom of God is sovereignly given by Christ. He gives it to his disciples by grace and withholds it from others in justice according to the eternal decree. God’s grace is sovereign and therefore unbelief is part of his plan to the praise of his glory.