From: Matthew 13:18-23
Parable of the Sower. The Meaning of the Parables (Continuation)
(Jesus said to His disciples,)  "Hear then the parable of the sower.  When any one hears the Word of the Kingdom and does not understand it, the evil one comes and snatches away what is sown in hies heart; this is what was sown along the path.  As for what was sown on rocky ground, this is he who hears the Word and immediately receives it with joy;  yet he has no root in himself, but endures for a while, and when tribulation or persecution arises on account of the Word, immediately he falls away.  As for what was sown among thorns, this is he who hears the Word, but the cares of the world and the delight in riches choke the Word, and it proves unfruitful.  As for what was sown on good soil, this is he who hears the Word and understands it; he indeed bears fruit, and yields, in one case a hundredfold, in another sixty, and in another thirty."
Chapter 13 of St. Matthew includes as many as seven of Jesus' parables, which is the reason why it is usually called "the parable discourse" or the "parabolic discourse". Because of their similarity of content and setting these parables are often called the "Kingdom parables", and also the "parables of the Lake", because Jesus taught them on the shore of Lake Gennesaret. Jesus uses these elaborate comparisons (parables) to explain certain features of the Kingdom of God which He has come to establish (cf. Matthew 3:2)--its tiny, humble origins; its steady growth; its worldwide scope; its salvific force. God calls everyone to salvation but only those attain it who receive God's call with good dispositions and who do not change their attitude; the value of the spiritual benefits the Kingdom brings--so valuable that one should give up everything to obtain them; the fact that good and bad are all mixed together until the harvest time, or the time of God's judgment; the intimate connection between earthly and heavenly as pects of the Kingdom, until it reaches its point of full development at the end of time.
On Jesus' lips, parables are exceptionally effective. By using parables He keeps His listeners' attention, whether they are uneducated or not, and by means of the most ordinary things of daily life He sheds light on the deepest supernatural mysteries. He used the parable device in a masterly way; His parables are quite unique; they carry the seal of His personality; through them He has graphically shown us the riches of grace, the life of the Church, the demands of the faith and even the mystery of God's own inner life.
Jesus' teaching continues to provide every generation with light and guidance on moral conduct. By reading and reflecting on His parables one can savor the adorable humanity of the Savior, who showed such kindness to the people who crowded around to hear Him--and who shows the same readiness to listen to our prayers, despite our dullness, and to reply to our healthy curiosity when we try to make out His meaning.
19. He does not understand because he does not love--not because he is not clever enough: lack of love opens the door of the soul to the devil.
Source: "The Navarre Bible: Text and Commentaries". Biblical text taken from the Revised Standard Version and New Vulgate. Commentaries made by members of the Faculty of Theology of the University of Navarre, Spain. Published by Four Courts Press, Kill Lane, Blackrock, Co. Dublin, Ireland. Reprinted with permission from Four Courts Press and Scepter Publishers, the U.S. publisher.