"Let burning coals fall on them. Let them be thrown into the fire, into miry pits, from where they never rise" (140:10). How can a psalm pray like this?

First, what the psalm says. These lines are prayed to the LORD. Before them the psalmist says, "I said to the LORD, “You are my God.”" (140:6), and "LORD, don’t grant the desires of the wicked" (140:8). He doesn't say he will do anything to these men himself. The first thing he asks is "let the mischief of their own lips cover them" (140:9). Then come the coals, the fire and the pits (140:10). In the WEB the next verse says what will happen rather than asking for it: "An evil speaker won’t be established on the earth. Evil will hunt the violent man to overthrow him" (140:11). Then it trusts the LORD to act: "I know that the LORD will maintain the cause of the afflicted, and justice for the needy" (140:12). The psalm names none of them, and these notes apply its words to no one today. Psalm 140 is not the only psalm that prays against enemies, and Christians read these prayers in more than one way. The chapter on Psalm 109 sets out the main readings, each resting on its verses, and chooses none. These notes don't choose either.