Jude 1:3 Beloved, although I was very eager to write to you about our common salvation, I found it necessary to write appealing to you to contend for the faith that was once for all delivered to the saints.
1Corinthians 15:17 And if Christ has not been raised, your faith is futile and you are still in your sins.
Throughout the New Testament Scriptures, we find a distinction in the way the New Testament authors talk about faith. Sometimes they talk about THE faith and sometimes they talk about YOUR faith.
When Jude writes to the beloved saints he does so acknowledging that they have a common salvation and appeals to them to contend for THE FAITH that was once and for all delivered to the saints. When he talks about the faith in this respect he is talking about all matters of truth that pertain to an understanding of the Christian faith. It is difficult to reduce this matter to the simple and irreducible message of the gospel, but the gospel is certainly the very center and thrust of the faith. The faith associated with our common salvation is surrounded by the historic setting and doctrines and life of the gospel upheld by and lived out in the church. There is one faith which is the faith and it alone is the basis for a common salvation that everyone in the faith obtains.
In other Scriptures we find the biblical authors showing that this faith must have an individual, personal component of ownership. It is my faith or your faith. When we read the personal pronouns associated with faith, we know that the biblical author is asking us to consider the individual belief we have in Jesus Christ that brings us into the faith in which we live. Paul tells the believers in Corinth that if Jesus has not been raised, their faith is in vain. In other words, their individual belief in Jesus would be for nothing if he has not conquered the grave to give us hope of our own future resurrection from the dead and life everlasting. Through faith in the risen Christ, we are saved.
The distinction is important because those who come to faith in Christ become responsible for the faith in which we stand. The faith delivered to the saints is delivered through them having faith in the Lord Jesus Christ. When we come to faith in Jesus Christ we become members of the corporate custodians of the faith to this world. Through the foundation of the apostles and prophets, and Christ himself, he has commissioned a succession of the faith to be upheld, protected, lived and proclaimed by the church. For those who have faith in Jesus, they do not just have an individual responsibility to trust in him, but are part of a corporate responsibility with all believers everywhere to uphold the faith with the integrity and purity that the gospel message demands. Every Christian who walks in a profession of faith has a weight of responsibility to contend for the faith in this world. We do it as a corporate body (the church) helping each other to live it, protect it, proclaim it, teach it, and uphold it in every way possible.