Jude was dealing with false teaching and false thinking that was infiltrating the church. His purpose is to motivate Christians to be faithful to their calling and to stand up for the truth of God’s Word. The phrase “contend earnestly” is one word in Greek and means to “fight” or “strive” or “go to battle”. This is serious. We are at war. War is costly. It require sacrifice, commitment, determination. We have to know what is at stake! Jude’s words are especially fitting in our modern world today. Our summary verse is from Jude 1:3: “Beloved, while I was very diligent to write to you concerning our common salvation, I found it necessary to write to you exhorting you to contend earnestly for the faith which was once for all delivered to the saints.” – (NKJV)

source https://burdenblessing.podbean.com/e/61-jude-summary-verse/