1 This Psalm's lintel is thus inscribed: “Unto the end, for Idithun, a Psalm to Asaph himself.” What “Unto the end” is, you know. Idithun is interpreted “leaping over those men,” Asaph is interpreted “a congregation.” Here therefore there is speaking “a congregation that leaps over,” in order that it may reach the End, which is Christ Jesus....
Source: The Enarrations, or Expositions, on the Psalms (New Advent)