The Parable of the Sower is a notable study of preaching, showing its differing effects and describing the diversity of hearers. The wayside hearers are legion. The soil lies all unprepared either by previous thought or prayer; as a consequence, the devil easily takes away the seed (which is the Word of God) and dissipating all good impressions, renders the work of the sower futile. No one for a moment believes, that so much of present-day sowing would go fruitless if only the hearers would prepare the ground of their hearts beforehand by prayer and meditation.

Similarly with the stony-ground hearers, and the thorny-ground hearers. Although the word lodges in their hearts and begins to sprout, yet all is lost, chiefly because there is no prayer or watchfulness or cultivation following. The good-ground hearers are profited by the sowing, simply because their minds have been prepared for the reception of the seed, and that, after hearing, they have cultivated the seed sown in their hearts, by the exercise of prayer. All this gives peculiar emphasis to the conclusion of this striking parable: “Take heed, therefore, how ye hear.” And in order that we may take heed how we hear, it is needful to give ourselves continually to prayer.

Source: E.M. Bounds in the Necessity of Prayer