Slay them not, lest my people forget: scatter them by thy power; and bring them down, O Lord our shield. Slay them not, lest my people forget - I believe the Chaldee gives the true sense of this verse: "Do not slay them suddenly, lest my people should forget. Drive them from their habitations by thy power, and reduce them to poverty by the loss of their property." Preserve them long in a state of chastisement that Israel may see thou hast undertaken for them: that thy hand is on the wicked for evil and on them for good. The Canaanites were not suddenly destroyed; they were left to be pricks in the eyes and thorns in the sides of the Israelites. It is in a sense somewhat similar that the words are used here.
Related Commentaries of Psalms 59:11
Psalms 59:11
11 Slay them not, lest my people forget: scatter them by thy power; and bring them down, O Lord our shield.