148 The Psalms recall to mind the truths revealed by God to the chosen people, which were at one time frightening and at another filled with wonderful tenderness; they keep repeating and fostering the hope of the promised Liberator which in ancient times was kept alive with song, either around the hearth or in the stately temple; they show forth in splendid light the prophesied glory of Jesus Christ: first, His supreme and eternal power, then His lowly coming to this terrestrial exile, His kingly dignity and priestly power and, finally, His beneficent labors, and the shedding of His blood for our redemption. In a similar way they express the joy, the bitterness, the hope and fear of our hearts and our desire of loving God and hoping in Him alone, and our mystic ascent to divine tabernacles.
Source: Mediator Dei (Vatican.va)