Albert Barnes Commentary Psalms 55:9

"Destroy, O Lord, [and] divide their tongue; For I have seen violence and strife in the city." — Psalms 55:9 (ASV)

Destroy, O Lord - The word translated “destroy,” properly means to “swallow up” or to “devour” with the idea of greediness (Isaiah 28:4; Exodus 7:12; Jonah 1:17; Jeremiah 51:34). It is then used in the sense of “destroy,” (Job 20:18; Proverbs 1:12).

The reference here is to the people who had conspired against David. It is a prayer that they, and their counsels, might be destroyed. This is the kind of prayer people always offer when they pray for victory in battle.

It is a prayer that they may be successful in what they regard as a righteous cause, but this implies a prayer that their enemies may be defeated and overcome. That is, they pray for success in what they have undertaken; and if it is right for them to attempt to do the thing, it is not wrong to pray that they may be successful.

And divide their tongues - There is a clear allusion here to the confusion of tongues at Babel (Genesis 11:1–9). Just as the language of those who undertook to build that tower was confounded so that they could not understand each other, so the psalmist prays that the counsels of those engaged against him might be confounded, or that they might be divided and distracted in their plans, so that they could not act in harmony. It is very probable that there is an allusion here to the prayer David offered when he learned that Ahithophel was among the conspirators (2 Samuel 15:31): And David said, O Lord, I pray thee, turn the counsel of Ahithophel into foolishness. This prayer would tend to divide and distract their counsels, frustrating the purposes of Absalom and securing his defeat.

For I have seen violence and strife in the city - This refers to Jerusalem. Perhaps David had learned that there was not complete harmony among the conspirators. Instead, there were elements of “strife” and discord that led him to hope their counsels would be confounded. There was little homogeneity of aim and purpose among Absalom’s followers. Perhaps David also knew enough about Ahithophel to see that his views, even though he might be enlisted in the cause of the rebellion, would not likely harmonize with the views of the general body of those engaged in the revolt.