Charles H. Spurgeon on Psalms 57:7

Sincerity makes the Christian sing, when he hath nothing to his supper. David was in none of the best case when in the cave, yet we never find him merrier: his heart makes sweeter music than ever his harp did. William Gurnall.

Verses 7-8. That worship that is performed with a sleepy, drowsy body, is a weak worship, but the psalmist here makes the awakening of the body to be the fruit and effect of the preparation of the heart; Awake up, my glory; awake, psaltery and harp: I myself will awake early. Why so? My heart is prepared. The heart prepared and thereby awaked, will awake the body. To worship God therefore without a prepared heart, is to worship him with a drowsy body, because with a drowsy heart, and therefore weakly. John Angier, in "An Help to Better Hearts, for Better Times," 1647.