Here’s a nice little excerpt at Speaking to the Soul today.
The image of water on rock is a favorite one that comes out of the Sayings of the Desert Fathers. Abba Poemen is one of the greater fathers who appears quite a bit in the Sayings, having a large collection of his own and appearing frequently in the sayings of others. According to Benedicta Ward, one-seventh of the sayings are his and his material may have formed the original core of the Sayings material. Here’s the full text from which the image comes as found in his saying 183:
Abba John, who had been exiled by the Emperor Marcian, said, “We went to Syria one day to see Abba Poemen and we wanted to ask him about purity of heart. But the old man did not know Greek and no interpreter could be found. So, seeing our embarrassment, the old man began to speak Greek saying, ‘The nature of water is soft, that of stone is hard; but if a bottle is hung above the stone, allowing the water to fall drop by drop, it wears away the stone. So it is with the word of God; it is soft and our heart is hard, but the man who hears the word of God often, opens his heart to the fear of God.'” (Ward, Sayings of the Desert Fathers, 192-3)