“Like a slug that dissolves in its slime”
Like a slug that dissolves in its slime, like a woman's stillborn child, may they never see the sun. (Psalm 58:8 BSB)
What it sounds like today
A random, almost comic comparison to a snail.
The cultural key
To modern eyes this is an odd, even funny image. It rests on an observation people once took literally. A snail or slug leaves a glistening trail behind it and appears to grow smaller as it goes, so it was widely believed the creature was slowly dissolving itself, melting away into its own slime until nothing was left. David turns that belief into an imprecation: may the wicked waste away like the snail that seems to consume itself as it crawls, until they simply cease to exist, paired with the stillborn child who 'never sees the sun.' The point is total disappearance, an enemy who shrinks to nothing and leaves no trace. The picture belongs with other dissolution imagery, like the wicked who 'melt like wax before the fire' (Psalm 68:2). Knowing the old folk belief turns a puzzling simile into a vivid curse of vanishing.
Recovered meaning
The simile draws on the ancient belief that a snail melts itself away into its slime trail as it moves. David curses the wicked to waste away just so, dwindling to nothing until they vanish like a snail or a stillborn child that never sees daylight.