But thou, O Lord, be merciful unto me - That is, give me strength; restore me from my sickness and weakness.
And raise me up - From my bed of languishing.
That I may requite them - That I may repay them; or may recompense them. The word used here - שׁלם shālam - means properly, to be whole, sound, safe; then, in Piel, to make secure, or preserve in safety; and then, to complete, to make whole, to make good, to restore; and then, to make whole or to complete in the sense of recompensing or requiting: to make the matter equal. It would be well expressed here by the familiar language, “giving them what they deserve.” But it is not necessary to understand this as indicating an unforgiving spirit. The writer may have meant to say that the persons who demeaned themselves in this manner ought to be punished; that the public good required it; and being a magistrate, he spoke as one appointed to administer the laws, and prayed for a restoration to strength, that he might administer justice in this and in all similar cases. It is possible also that he meant to say he would repay them by “heaping coals of fire on their heads” - by acts of kindness in place of the wrongs that they had done him (see Proverbs 25:21-22; compare Romans 12:20-21); though I admit, that this is not the obvious interpretation. But in order to show that this was uttered with a bad spirit, and under the promptings of revenge, it would be necessary to show that neither of these supposable interpretations could be the true one. It may be added here that we may not be required to vindicate all the expressions of personal feeling found in the Psalms in order to any just view of inspiration. See General Introduction, 6 (6).