Here to be "in the light" is a metaphor for doing what is right. Alternate translation: "he does what is right" (See: [[rc://en/ta/man/jit/figs-metaphor]])
Here to be "in the darkness" is a metaphor for doing what is evil. Alternate translation: "does what is evil" (See: [[rc://en/ta/man/jit/figs-metaphor]])