Psalms 137:6

If I do not remember thee - Equivalent to, “If I forget thee.” If I ever fail to remember thee; if I shall ever act as if I had forgotten thee. Singing in a strange land, among those who had perpetrated such wrongs in thee - appearing to be happy, cheerful, joyous, happy, merry there - would be understood to imply that I had ceased to remember thee, and cared nothing for thee.

Let my tongue cleave to the roof of my mouth - Compare Ezekiel 3:26. Let me be unable to speak; let my tongue be as it were attached to the upper part of the mouth, so that it could not be used. If I employ it in an unworthy purpose - in any way whereby it can be inferred that I have ceased to remember my native land, and the city of our solemnities, let my tongue be ever after useless. This language is often employed by Virgil: Vox faucibus haesit.

If I prefer not Jerusalem - literally, “If I do not cause to ascend.” That is, If I do not exalt Jerusalem in my estimation above everything that gives me pleasure; if I do not find my supreme happiness in that.

Above my chief joy - Margin, as in Hebrew, the head of my joy. The chief thing which gives me joy; as the head is the chief, or is supreme over the body. This is expressive of a great truth in regard to religion. Anything else - everything else - is to be sooner sacrificed than that. The happiness which is found in religion is superior to that found in every other source of enjoyment, and is preferred to every other. If either is to be sacrificed - the joy of religion, or the pleasure derived from society, from the frivolous world, from literature, from music, from dancing, from works of art - it will be the latter and not the former. There are other sources of joy which are not in any way inconsistent with religion: the joy of friendship; of domestic life; of honorable pursuits of the esteem of people. So of music, the arts, gardens, literature, science. But when one interferes with the other, or is inconsistent with the other, the joy of the world is to be sacrificed to the joy of religion. When the joy of religion is sacrificed for the joy of the world, it proves that there is no true piety in the soul. Religion, if it exists at all, will always be supreme.