The tongue is a metonym for what people say. James calls it a fire because of the great damage it can do. Alternate translation: "The tongue is like a fire" (See: [[rc://en/ta/man/translate/figs-metonymy]] and [[rc://en/ta/man/translate/figs-metaphor]])
The writer speaks metaphorically of the way a person becomes unacceptable to God when he speaks sinful words as if the person's words made stains on his body. (See: [[rc://en/ta/man/translate/figs-metaphor]])
The phrase "course of life" refers to a person's entire life. Alternate translation: "it ruins a person's entire life" (See: [[rc://en/ta/man/translate/figs-metaphor]])
The word "itself" refers to the tongue. Also, here "hell" refers to the powers of evil or to the devil. This can be stated in active form. Alternate translation: "life because the devil uses it for evil" (See: [[rc://en/ta/man/translate/figs-activepassive]] and [[rc://en/ta/man/translate/figs-metaphor]])