Psalm 137:1
137:1 By the rivers of Babylon, there we {a} sat down, yea, we
      wept, when we remembered Zion.

      (a) That is, we abode a long time, and even though the
          country was pleasant, yet it could not stay our tears,
          nor turn us from the true service of our God.

Psalm 137:2
137:2 We hanged our harps upon the willows in the midst {b}
      thereof.

      (b) That is, of that country.

Psalm 137:3
137:3 For there they that carried us away captive {c} required
      of us a song; and they that wasted us [required of us]
      mirth, [saying], Sing us [one] of the songs of Zion.

      (c) The Babylonians speak thus in mocking us, as though by
          our silence we should signify that we hoped no more in
          God.

Psalm 137:5
137:5 {d} If I forget thee, O Jerusalem, let my right hand
      forget [her cunning].

      (d) Even the faithful are touched by their particular
          griefs, yet the common sorrow of the Church is most
          grievous to them, and is such as they cannot but
          remember and lament.

Psalm 137:6
137:6 If I do not remember thee, let my tongue cleave to the
      roof of my mouth; if I prefer not Jerusalem above my {e}
      chief joy.

      (e) The decay of God's religion in their country was so
          grievous that no joy could make them glad, unless it
          was restored.

Psalm 137:7
137:7 Remember, O LORD, the children of {f} Edom in the {g} day
      of Jerusalem; who said, Rase [it], rase [it, even] to the
      foundation thereof.

      (f) As was prophesied in Ezekiel 25:13,Jeremiah 49:7,Obadiah 1:10,
          showing that the Edomites who came from Esau,
          conspired with the Babylonians against their brethren
          and kinsfolk.
      (g) When you visited Jerusalem.

Psalm 137:9
137:9 {h} Happy [shall he be], that taketh and dasheth thy
      little ones against the stones.

      (h) He alludes to Isaiah's prophecy in Isaiah 13:16
          promising good success to Cyrus and Darius, whom
          ambition moved to fight against Babylon, but God used
          them as his rods to punish his enemies.