What does Psalm 35:6 mean?

Depending on weather and time of day, a trail might be dry and well lit. When the same path is poorly lit, muddy, or waterlogged, it becomes far more treacherous. Anyone who has hiked through natural terrain knows terms like "slippery" and "dark" are serious in those situations. They put a traveler in constant jeopardy of losing balance. This could cause a fall, an injury, or even death. In the worst scenario it could mean falling over a cliff or ledge.

This is one of the "imprecatory psalms" which include prayers for God to actively attack one's enemies. The context of this request has been David's plea for help using terms related to physical battle (Psalm 35:1–5). Scripture often uses the metaphor of a person's path to refer to their life (Psalm 17:5) and treats "light" as the embodiment of truth and goodness (Psalm 119:105). It's no small thing for David to ask God to create a dark, slippery way for his enemies.

Further, he wants "the angel of the LORD" to pursue them. Being pursued would make the trail even more hazardous for David's enemies. The angel of the Lord is described in Psalm 34:7 as protecting those who fear the Lord (Proverbs 1:7) and delivering them from trouble. Here, this angel is depicted as chasing the wicked to judgment. It is far better to run to the Lord for salvation than to run from Him into judgment (Hebrews 10:30–31)!