A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
psa 12:1On title, see Introduction and see on Psa 6:1. The Psalmist laments the decrease of good men. The pride and deceit of the wicked provokes God's wrath, whose promise to avenge the cause of pious sufferers will be verified even amidst prevailing iniquity. (Psa 12:1-8)
the faithful--or literally, "faithfulness" (Psa 31:23).
psa 12:2The want of it is illustrated by the prevalence of deceit and instability.
psa 12:3Boasting (Dan 7:25) is, like flattery, a species of lying.
lips, and . . . tongue--for persons.
psa 12:5The writer intimates his confidence by depicting God's actions (compare Psa 9:19; Psa 10:12) as coming to save the poor at whom the wicked sneer (Psa 10:5).
psa 12:6The words--literally, "saying of" (Psa 12:5).
seven times--thoroughly (Dan 3:19).
psa 12:8The wicked roam undisturbed doing evil, when vileness and vile men are exalted.