John Trapp on Psalms 40:15

Verſ. 15. Let them be deſolate for a reward] a poor reward; but ſuch as ſin payeth to her ſervants; the wages of ſin is death. Sin payeth all her ſervants in black mony. See Pſal. 35.21. The ward here rendred reward, ſignifieth an heel. It is, as if the Prophet ſhould ſay, Let one deſolation tread upon the heels of another, [illegible: 1 letter]ill they be utterly undone.