Jude 1:3

3 I found it necessary. Instead of the doctrinal treatise he had intended to write, Jude feels compelled to address the problem of false teachers (v. 4). We do not know whether his original intention was fulfilled at some other time.

contend for the faith. Here “faith” indicates the content of the message taught by the apostles and held in common by all Christians, rather than the personal exercise of trust by a believer. Christianity includes an authoritative body of belief given by God to the church through the apostles (1 Cor. 15:3–8). Together with the Old Testament (Eph. 2:20), this apostolic witness, as found in the New Testament, is the standard for the church (2 John 9, 10).