10 “Juda is my king: Moab the pot of my hope”. What Juda? He that is of the tribe of Juda. What Juda, but He to whom Jacob himself said, “Juda, your brethren shall praise you”? What therefore should I fear, when Juda my king says, “Fear not them that kill the body”? “Moab the pot of my hope.” Wherefore “pot”? Because tribulation. Wherefore “of my hope”? Because there has gone before Juda my king....Moab is perceived in the Gentiles. For that nation was born of sin, that nation was born of the daughters of Lot, who lay with their father drunken, abusing a father.
Better were it to have remained barren, than thus to have become mothers. But this was a kind of figure of them that abuse the law. For do not heed that law in the Latin language is of the feminine gender: in Greek of the masculine gender it is: but whether it be of the feminine gender in speaking, or of the masculine, the expression makes no difference to the truth. For law has rather a masculine force, because it rules, is not ruled. But moreover, the Apostle Paul says what?
“Good is the law, if any one use it lawfully.” But those daughters of Lot unlawfully used their father. But in the same manner as good works begin to grow when a man uses well the law: so arise evil works, when a man ill uses the law. Furthermore, they ill using their father, that is, ill using the law, engendered the Moabites, by whom are signified evil works. Thence the tribulation of the Church, thence the pot boiling up. Of this pot in a certain place of prophecy is said, “A pot heated by the North wind.” Whence but by the quarters of the devil, who has said, “I will set my seat at the North”? The chiefest tribulations therefore arise against the Church from none except from those that ill use the law....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)