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. For certain men have crept in unnoticed, who long ago were marked out for this condemnation, ungodly men, who turn the grace of our God into lewdness and deny the only Lord God and our Lord Jesus Christ. (Jude 1:3-4)
What is meant by “faith once delivered unto the saints”? This Christian faith has been once for all delivered to the saints, nothing to be added to it or taken from it. God’s supreme revelation through Jesus Christ concerning the teaching of the Christian faith is finished. In the context of Jude 1:3, faith is not referring to the belief, trust or confidence which Christians have in God, but to the embodiment of doctrine which was given to the church by Jesus and the apostles. There is a body of Christian doctrine that is called “the faith once delivered.”
Our only infallible source of authority is Jesus. Anyone who claims to have a new revelation from God in order to add to the faith once for all delivered to the saints is against Christ. Jesus also gave unique authority to the apostles. Jesus said to the apostles, “Howbeit when he, the Spirit of truth, is come, he will guide you into all truth” (John 16:13). Jesus told the apostles that the Spirit would guide them into all truth. In other words, the apostles were guided into all truth through the Holy Spirit when they wrote Scripture.
John the Apostle wrote, “Let that therefore abide in you, which ye have heard from the beginning. If that which ye have heard from the beginning shall remain in you, ye also shall continue in the Son, and in the Father” (1 John 2:24). Continuing in the Son and the Father is dependent upon the apostolic faith remaining in us. There was an established faith which was taught by the apostles “from the beginning.” Deviation from that apostolic faith to something new is a departure from the faith.