Paul was clear about what he believed patriotism involved for those who are Christians. His use of “fight the good fight” is a patriotic warfare idiom for one who perseveres in loyalty to King and heavenly country by fighting war campaigns to preserve the welfare of the God’s kingdom on earth. In this way a person earns a reputation as a good and honorable citizen in God’s kingdom.
The expression “fight the good fight” is often used in Christian circles and even in Western culture in general. Indeed, while perusing Amazon.com I found at least thirty-one books with the title “The Good Fight” and at least ten books with the fuller title “Fighting the Good Fight,” some of which were overtly Christian but many of which were not. The origin of the phrase is 1 Timothy 1:18 (and perhaps in 1 Tim. 6:12 and 2 Tim. 4:7). In 1 Timothy 1:18 and 6:12, Timothy is exhorted to “fight the good fight”; in 2 Timothy 4:7, Paul says that he himself “has fought the good fight.”