Abba Poemen said: The nature of water is yielding, and that of a stone is hard. Yet if you hang a bottle filled with water above the stone so that the water drips drop by drop, it will wear a hole in the stone. In the same way the word of God is tender, and our heart is hard. So when people hear the word of God frequently, their hearts are opened to the fear of God.
--from Desert Wisdom by Yushi Nomura and Henri Nouwen