One expects a spring or fountain to have clear water, just as one expects a righteous man to stand for what he believes. A polluted spring or fountain is compared to a righteous man who falls. (See: [[rc://en/ta/man/jit/figs-simile]])
Tottering is a metaphor for either 1) refusing to fight wicked people or 2) joining in their wickedness. Alternate translation: "who allows wicked people to do wickedness" or "who starts to do what wicked people do" (See: [[rc://en/ta/man/jit/figs-metaphor]])