Paul uses this word to contrast the lazy believers with the hardworking believers.
The word “you” refers to all the Thessalonian believers. (See: rc://en/ta/man/translate/figs-you)
Here “brothers” means fellow Christians, including both men and women. AT: “brothers and sisters” (See: rc://en/ta/man/translate/figs-gendernotations)
To “lose heart” is an idiom that means to get tired, weary, or discouraged. AT: “do not be discouraged” or “do not grow weary” (See: rc://en/ta/man/translate/figs-idiom)
“Word” here is a synecdoche for “message” or “teaching.” AT: “if anyone does not obey our instructions” (See: rc://en/ta/man/translate/figs-synecdoche)
Notice who he is. AT: “publicly identify that person” (See: rc://en/ta/man/translate/figs-idiom)
Paul instructs believers to shun lazy believers as a disciplinary action.