2 Observe “the waters of Babylon.” “The waters of Babylon” are all things which here are loved, and pass away. One man, for example, loves to practise husbandry, to grow rich thereby, to employ his mind therein, thence to gain pleasure: let him observe the issue, and see that what he has loved is not a foundation of Jerusalem, but a stream of Babylon. Another says, It is a grand thing to be a soldier: all husbandmen fear those who are soldiers....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)