8 I will, therefore, says he, live separate with a few good men: why should I live in common with crowds? Well: those very few good men, from what crowds have they been strained out? If however these few are all good: it is, nevertheless, a good and praiseworthy design in man, to be with such as have chosen a quiet life; distant from the bustle of the people, from noisy crowds, from the great waves of life, they are as if in harbour. Is there therefore here that joy?
That jubilant gladness which is promised? Not as yet; but still groans, still the anxiety of temptations. For even the harbour has an entrance somewhere or other; if it had not, no ship could enter it; it must therefore be open on some side: but at times on this open side the wind rushes in; and where there are no rocks, ships dashed together shatter one another. Where then is security, if not even in harbour? And yet it must be confessed, it is true, that persons in harbour are in their degree much better off than when afloat on the main.
Let them love one another, as ships in harbour, let them be bound together happily; let them not dash against one another: let absolute equality be preserved there, constancy in love; and when perchance the wind rushes in from the open side, let there be careful piloting there. Now what will one who perchance presides over such places, nay, who serves his brethren, in what are called monasteries, tell me? I will be cautious: I will admit no wicked man. How will you admit no evil one?...Those who are about to enter, do not know themselves; how much less do you know them?
For many have promised themselves that they were about to fulfil that holy life, which has all things in common, where no man calls anything his own, who have one soul and one heart in God: they have been put into the furnace, and have cracked. How then do you know him who is unknown even to himself?...Where then is security? Here nowhere; in this life nowhere, except solely in the hope of the promise of God. But there, when we shall reach thereunto, is complete security, when the gates are shut, and the bars of the gates of Jerusalem made fast; there is truly full jubilance, and great delight. Only do not thou feel secure in praising any sort of life: “judge no man blessed before his death.”
Source: The Enarrations, or Expositions, on the Psalms (New Advent)