We hanged our harps upon the willows - The ערבים arabim or willows were very plentiful in Babylon. The great quantity of them that were on the banks of the Euphrates caused Isaiah, Isaiah 15:7, to call it the brook or river of willows. This is a most affecting picture. Perhaps resting themselves after toil, and wishing to spend their time religiously, they took their harps, and were about to sing one of the songs of Zion; but, reflecting on their own country, they became so filled with distress, that they unstrung their harps with one consent, and hung them on the willow bushes, and gave a general loose to their grief. Some of the Babylonians, who probably attended such meetings for the sake of the music, being present at the time here specified, desired them to sing one of Zion's songs: this is affectingly told.

we hanged. Willows were so plentiful at Babylon on the banks of the Euphrates, that Isaiah calls it the brook or river of willows.

Psalm 33:2 Praise the LORD with harp: sing to him with the psaltery and an instrument of ten strings.

Psalm 81:2 Take a psalm, and bring here the tambourine, the pleasant harp with the psaltery.

Isaiah 24:8 The mirth of tabrets ceases, the noise of them that rejoice ends, the joy of the harp ceases.

Ezekiel 26:13 And I will cause the noise of your songs to cease; and the sound of your harps shall be no more heard.

Amos 8:10 And I will turn your feasts into mourning, and all your songs into lamentation; and I will bring up sackcloth on all loins...

Revelation 18:22 And the voice of harpers, and musicians, and of pipers, and trumpeters, shall be heard no more at all in you; and no craftsman...

Thou Shalt not Commit Adultery.
In this Commandment too a good work is commanded, which includes much and drives away much vice; it is called purity, or chastity, of which much is written and preached, and it is well known to every one, only that it is not as carefully observed and practised as other works which are not commanded. So ready are we to do what is not commanded and to leave undone what is commanded. We see that the world is full of shameful works of unchastity, indecent words, tales and ditties, temptation to which …
Dr. Martin Luther—A Treatise on Good Works

Psalms
The piety of the Old Testament Church is reflected with more clearness and variety in the Psalter than in any other book of the Old Testament. It constitutes the response of the Church to the divine demands of prophecy, and, in a less degree, of law; or, rather, it expresses those emotions and aspirations of the universal heart which lie deeper than any formal demand. It is the speech of the soul face to face with God. Its words are as simple and unaffected as human words can be, for it is the genius …
John Edgar McFadyen—Introduction to the Old Testament