We now come within the final collection of Davidic psalms (Psalm 138-145) to its central sequence of five prayers in which David seeks deliverance from wicked enemies (140-144). The first of these, Psalm 140, is a lamenting plea for preservation from the plotting of evil, violent men and a call for divine retribution. The structure of the psalm is easy to discern. There are four stanzas (verses 1-3, 4-5, 6-8, 9-11), the first three ending with "Selah" and the last followed by a two-verse conclusion (verses 12-13).
The first two stanzas set up the problem David is faced with. It is interesting to note that the same words are used for the second line in both the first and second stanzas: "Preserve me from violent men" (verses 1, 4). The violent here may intend physical brutality, but their method of attack is verbal—through deceit and slander (see verse 3; compare verses 9, 11). David experienced a number of such incidents in his life.
In the third stanza, David says he has appealed to the Lord in complete trust (verse 6-7). He knows that the One who has "covered" or shielded (NIV) his head in actual physical battles will protect him in this current "battle" (verse 7). With this confidence, he asks that God not grant success to the schemes of his enemies (verse 8). As noted in regard to the previous psalm, Jesus' instruction in the New Testament to bless and pray for our enemies (Matthew 5:44 Matthew 5:44But I say to you, Love your enemies, bless them that curse you, do good to them that hate you, and pray for them which spitefully use you, and persecute you;
American King James Version×) does not mean praying for their success in opposing and harming us.
In the fourth stanza David calls for a curse on the offenders. Whereas God covered or protected David's head in past battles (again, see verse 7), David calls for the head of his enemies to be covered only with the evil of their own lips—that is, for their scheming and slander against him to come back on them. Indeed, this is the decreed penalty in the law for bearing false witness against another (see Deuteronomy 19:16-21 Deuteronomy 19:16-21  If a false witness rise up against any man to testify against him that which is wrong;
 Then both the men, between whom the controversy is, shall stand before the LORD, before the priests and the judges, which shall be in those days;
 And the judges shall make diligent inquisition: and, behold, if the witness be a false witness, and has testified falsely against his brother;
 Then shall you do to him, as he had thought to have done to his brother: so shall you put the evil away from among you.
 And those which remain shall hear, and fear, and shall from now on commit no more any such evil among you.
 And your eye shall not pity; but life shall go for life, eye for eye, tooth for tooth, hand for hand, foot for foot.
American King James Version×). David as God's prophet is pronouncing this judgment. In another psalm, David foretold that burning coals and fire would rain down on the wicked (Psalms 11:6 Psalms 11:6On the wicked he shall rain snares, fire and brimstone, and an horrible tempest: this shall be the portion of their cup.
American King James Version×), as Sodom and Gomorrah experienced (Genesis 19:24 Genesis 19:24Then the LORD rained on Sodom and on Gomorrah brimstone and fire from the LORD out of heaven;
American King James Version×). Here that same penalty is called for (Psalms 140:10 Psalms 140:10Let burning coals fall on them: let them be cast into the fire; into deep pits, that they rise not up again.
American King James Version×), though the sense may be figurative of a calamitous divine judgment. As David's enemies tried to trip him up to cause him to fall into traps (verse 5), David calls for them to fall into deep pits "that they rise not up again" (verse 10). This too may be figurative—of being sunk into ineffectiveness. If it implies their deaths, then their not rising again would refer to them no longer being alive to cause trouble in the present world—not to them never being in a future resurrection. The next psalm likewise calls for the wicked to fall into their own nets (Psalms 141:9-10 Psalms 141:9-10  Keep me from the snares which they have laid for me, and the gins of the workers of iniquity.  Let the wicked fall into their own nets, whilst that I with escape.
American King James Version×).
David ends Psalm 140 in verses 12-13 on a confident note, assured that God will bring justice to the needy and afflicted and that God's people will dwell with Him in perpetual gratitude.