John Calvin Commentary Psalms 120:3

"What shall be given unto thee, and what shall be done more unto thee, Thou deceitful tongue?" — Psalms 120:3 (ASV)

What shall the tongue of deceit give thee? The Prophet aggravates the malice of his enemies by asserting that they were so wickedly inclined as to be driven to evil speaking when they saw no prospect of gaining any advantage from such behavior. However, he seems to express more than this — he seems further to imply that after they have poured out all the venom of their slanders, their attempts will nevertheless be vain and ineffectual.

Since God is the defender of the innocence of His servants, David, inspired with hope by this truth, rises up against them with heroic courage, as if about to triumph over all his slanderers, reproaching them for doing nothing more than betraying an impotent passion for evil speaking, which God, in the end, would cause to recoil upon their own heads.

This is a thought well suited to soothe the grief of all the godly when their good name is unjustly wounded by slanderers: such malicious people will gain nothing by it in the end, because God will disappoint their expectation.