Jude points us to a body of belief, a summary of "the faith that was once for all delivered to the saints," that was established early on in the life of the early church . Where can we find this summary today? Here it is, The Apostles Creed:

We believe in God the Father Almighty, Maker of heaven and earth; and in Jesus Christ his only Son our Lord, who was conceived by the Holy Spirit, born of the virgin Mary, suffered under Pontius Pilate, was crucified, died, and was buried. He descended into hell. The third day he rose again from the dead. He ascended into heaven, and is seated at the right hand of God the Father Almighty; from there he will come to judge the living and the dead. We believe in the Holy Spirit, the holy catholic church, the communion of saints, the forgiveness of sins, the resurrection of the body, and the life everlasting.