My wounds stink - The word rendered “wounds” here means properly the swelling or wales produced by stripes. See the notes at Isaiah 1:6; notes at Isaiah 53:5. The meaning here is, that he was under chastisement for his sin; that the stripes or blows on account of it had not only left a mark and produced a swelling, but that the skin itself had been broken, and that the flesh had become corrupt, and the sore offensive. Many expositors regard this as a mere figurative representation of the sorrow produced by the consciousness of sin; and of the loathsome nature of sin, but it seems to me that the whole connection rather requires us to understand it of bodily suffering, or of disease.
And are corrupt - The word used here - מקק mâqaq - means properly to melt; to pine away; and then, to flow, to run, as sores and ulcers do. The meaning here is, My sores run; to wit, with corrupt matter.
Because of my foolishness - Because of my sin, regarded as folly. Compare the notes at Psalms 14:1. The Scripture idea is that sin is the highest folly. Hence, the psalmist, at the same time that he confesses his sin, acknowledges also its foolishness. The idea of sin and that of folly become so blended together - or they are so entirely synonymous - that the one term may be used for the other.