On the dry stick which, at the bidding of his senior, Abbot John kept on watering as if it would grow:

And so this blessed John from his youth up even to a full and ripe age of manhood was subject to his senior as long as he continued living in this world, and carried out his commands with such humility that his senior himself was utterly astounded at his obedience; and as he wanted to make sure whether this virtue came from genuine faith and profound simplicity of heart, or whether it was put on and as it were constrained and only shown in the presence of the bidder, he often laid upon him many superfluous and almost unnecessary or even impossible commands. From which I will select three to show to those who wish to know how perfect was his disposition and subjection. For the old man took from his woodstack a stick which had previously been cut and got ready to make the fire with, and which, as no opportunity for cooking had come, was lying not merely dry but even mouldy from the lapse of time. And when he had stuck it into the ground before his very eyes, he ordered him to fetch water and to water it twice a day that by this daily watering it might strike roots and be restored to life as a tree, as it was before, and spread out its branches and afford a pleasant sight to the eyes as well as a shade for those who sat under it in the heat of summer. And this order the lad received with his customary veneration, never considering its impossibility, and day by day carried it out so that he constantly carried water for nearly two miles and never ceased to water the stick; and for a whole year no bodily infirmity, no festival services, no necessary business (which might fairly have excused him from carrying out the command), and lastly no severity of winter could interfere and hinder him from obeying this order. And when the old man had watched this zeal of his on the sly without saying anything for several days and had seen that he kept this command of his with simple willingness of heart, as if it had come from heaven, without any change of countenance or consideration of its reasonableness--approving the unfeigned obedience of his humility and at the same time commiserating his tedious labour which in the zeal of his devotion he had continued for a whole year--he came to the dry stick, and "John," said he, "has this tree put forth roots or no?" And when the other said that he did not know, then the old man as if seeking the truth of the matter and trying whether it was yet depending on its roots, pulled up the stick before him with a slight disturbance of the earth, and throwing it away told him that for the future he might stop watering it.

SAINT JOHN CASSIAN ON THE INSTITUTES OF THE COENOBIA AND THE REMEDIES FOR THE EIGHT PRINCIPAL FAULTS, BOOK IV, CHAPTER XXIV.