A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown [1882] at sacred-texts.com
Psalms Chapter 140
The style of this Psalm resembles those of David in the former part of the book, presenting the usual complaint, prayer, and confident hope of relief. (Psa 140:1-13)
evil man--Which of David's enemies is meant is not important.
This character of the wicked, and the devices planned against the pious, correspond to Psa 10:7; Psa 31:13; Psa 58:4, &c.
sharpened . . . like a serpent--not like a serpent does, but they are thus like a serpent in cunning and venom.
snare [and] net--for threatening dangers (compare Psa 38:12; Psa 57:6).
(Compare Psa 5:1-12; Psa 16:2).
day of battle--literally, "of armor," that is, when using it.
(Compare Psa 37:12; Psa 66:7).
lest they exalt themselves--or, they will be exalted if permitted to prosper.
Contrasts his head covered by God (Psa 140:7) with theirs, or (as "head" may be used for "persons") with them, covered with the results of their wicked deeds (Psa 7:16).
(Compare Psa 11:6; Psa 120:4).
cast into the fire; into deep pits--figures for utter destruction.
an evil speaker--or, "slanderer" will not be tolerated (Psa 101:7). The last clause may be translated: "an evil (man) He (God) shall hunt," &c.
(Compare Psa 9:4).
After all changes, the righteous shall have cause for praise. Such
shall dwell--shall sit securely, under God's protection (Psa 21:6; Psa 41:12).