The Sower went out to sow his seed; and as he sowed, some fell by the way side, and was trampled upon, and the birds of heaven devoured it. Luke 8:4
And as to the cause of the seed on the pathways being snatched away, we see in a moment that it is the hardness of the ground. A pathway always is hard and untilled, because it is exposed to every one’s feet, nor is any seed admitted into it, but lies rather upon the surface, ready for any birds that will to snatch it away. All those therefore, whose mind is hard and unyielding, and so to speak, pressed together, do not “receive the divine seed: for the divine and sacred admonition finds no entrance into them, nor do they accept the words that would produce in them the fear of God, and by means of which they could bring forth as fruits the glories of virtue. They have made themselves a beaten and trampled pathway for unclean demons, yea, and for Satan himself, such as never can bear holy fruit. Let those therefore awake, whose heart is sterile and unfruitful: open your mind, receive the sacred seed, be like productive and well-tilled soil, bring forth unto God the fruits that will raise you to an incorruptible life: guard your mind, shut the entrance against the thief, drive away from your hearts the flocks of birds, in order that the seed may abide with you; that ye may be ground luxuriant in corn, and very fertile, and rich abundantly in bringing forth fruit.
St. Cyril of Alexandria, Commentary on Luke, Homily XLI.