3 needful. The word “needful” connotes a sense of urgency. Jude had been planning to write a straightforward exposition of the doctrines associated with the “common salvation”—that is, the great salvation held in common by all who had been “sanctified,” “preserved,” and “called” (Jude 1). Instead, however, the Holy Spirit constrained and compelled him to write in defense of the faith which even then was under intense Satanic attack.
3 earnestly contend. Used only this once in the New Testament, “earnestly contend” is from the Greek epagonizomai. It was used of athletes intensely agonizing in the grueling training for a coming contest. Jude thus graphically stresses the urgency of defending the faith. Note also Philippians 1:7, 17; I Timothy 6:19-20; II Timothy 4:1-4; Titus 1:9; I Peter 3:15. The defense of the gospel is no indifferent matter, to be left to a few specialists, but one to which all believers should be trained and committed.
3 the faith. “The faith” is not in reference to the simple trust we place in Christ in salvation, but to the entire body of Christian truth as revealed in the Holy Scriptures.