John Gill Commentary Psalms 38:5

"My wounds are loathsome and corrupt, Because of my foolishness." — Psalms 38:5 (ASV)

My wounds stink, [and] are corrupt
Meaning his sins, which had wounded him, and for which there is no healing but in a wounded Saviour, and by his stripes we are healed, (Isaiah 53:5) ; where the same word is used as here; Christ's black and blue stripes and wounds, as the word signifies, are the healing of ours, both of sins, and of the effects of them; which, to a sensible sinner, are as nauseous and loathsome as an old wound that is festered and corrupt;

because of my foolishness :
as all sin arises from foolishness, which is bound in the hearts of men, and from whence it arises, (Mark 7:22) ; perhaps the psalmist may have respect to his folly with Bathsheba, which had been the occasion of all the distress that is spoken of both before and afterwards.