What does Psalm 40:2 mean?

Scripture does not record any literal events in David's life such as being trapped in a pit. Rather, this is additional poetry describing how deeply desperate was David's plight. David's warlike life was full of near-death experiences, some of which seemed so hopeless that they were like being in a trash pit or slimy swamp. One can imagine being abandoned in a cavernous hole in the ground filling with water, mud, and slime. In such a predicament it is impossible to get a foothold, but the Lord reached down to David, answered his cry for help, and pulled him to safety. David says the Lord set his feet on a rock and made his steps secure. The imagery indicates that the Lord rescued David from his enemies and provided security for him.

The patriarch Joseph experienced the calamity of being thrown into a pit, in a very literal sense. His brothers despised him and tried to get rid of him by putting him into a pit. However, in God's providence, Judah, one of the brothers, persuaded the others to draw him out of the pit and sell him to a caravan of Ishmaelites bound for Egypt. The brothers received twenty shekels of silver from the traders (Genesis 37:12–28).