In the family of Christian churches, some types are not so comfortable referring to “old stuff” because they are concerned with relying on traditional things held onto by rote without understand. And there are some that are much more comfortable referring back to “old stuff” like creeds and confessions. In either case, we probably could all agree the key is to understand these things and not merely to recite them without reflection.
One of the oldest statements about what we believe is the Nicene Creed.
The short story of the Nicene Creed is that in 325 AD, the church gathered in a council in the city of Nicaea to clarify confusion regarding the divinity of Jesus. A longer version of its history can be found at Wikipedia and Theopedia and certainly one can consult church history textbooks for much more comprehensive discussions. Below is an English translation of the creed
We believe in one God, the Father, the Almighty, maker of heaven and earth, of all that is, seen and unseen.
We believe in one Lord, Jesus Christ, the only Son of God, eternally begotten of the Father, God from God, Light from Light, true God from true God, begotten, not made, of one Being with the Father; through him all things were made. For us and for our salvation he came down from heaven, was incarnate of the Holy Spirit and the virgin Mary and became truly human. For our sake he was crucified under Pontius Pilate; he suffered death and was buried. On the third day he rose again in accordance with the Scriptures; he ascended into heaven and is seated at the right hand of the Father. He will come again in glory to judge the living and the dead, and his kingdom will have no end.
We believe in the Holy Spirit, the Lord, the giver of life, who proceeds from the Father and the Son, who with the Father and the Son is worshiped and glorified, who has spoken through the prophets. We believe in one holy catholic and apostolic Church. We acknowledge one Baptism for the forgiveness of sins. We look for the resurrection of the dead, and the life of the world to come. Amen.
Image at the top is of Uppsala Cathedral in Sweden.