"nothing will cause him to stumble." The word "stumbling" is a metaphor that means to fail spiritually or morally. AT: "nothing will cause him to sin" or "he will not fail to do what is pleasing to God" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here "walk" is a metaphor for how a person lives or behaves. Here to be "in the darkness" and "walks in the darkness" mean the same thing. This brings attention to how evil it is to hate a fellow believer. AT: "does what is evil" (See: [[rc://en/ta/man/translate/figs-metaphor]] and [[rc://en/ta/man/translate/figs-parallelism]])
This is a metaphor for the believer who is not living as a Christian should be living. AT: "he does not know what he should do" (See: [[rc://en/ta/man/translate/figs-metaphor]])
"the darkness has made him unable to see." Darkness is a metaphor for sin or evil. AT: "sin has made it impossible for him to understand the truth" (See: [[rc://en/ta/man/translate/figs-metaphor]])