Explanatory Notes on the Whole Bible, by John Wesley, [1754-65], at sacred-texts.com
  
Psalms 12:4
 
psa 12:4
Prevail - By raising and spreading evil reports concerning him. Our own - At our own disposal to speak what we please, who can control or restrain us? 
Psalms 12:5
 
psa 12:5
Puffeth - From him that despises him, and hopes to destroy him with a puff of breath. 
Psalms 12:6
 
psa 12:6
Pure - Without the least mixture of falsehood; and therefore shall infallibly be fulfilled. 
Psalms 12:7
 
psa 12:7
Thou shalt keep them - Thy words or promises: these thou wilt observe and keep, both now, and from this generation for ever. 
Psalms 12:8
 
psa 12:8
Walk - They fill all places, and go about boldly and securely.